CN106664280B

CN106664280B - Method and apparatus for transceiving data in wireless communication system

Info

Publication number: CN106664280B
Application number: CN201580037076.4A
Authority: CN
Inventors: 朴钟贤; 安俊基; 徐翰瞥; 李承旻; 李润贞
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2014-07-07
Filing date: 2015-07-06
Publication date: 2020-02-28
Anticipated expiration: 2035-07-06
Also published as: CN106664280A; JP2017526218A; US10595310B2; US20170208588A1; EP3169029A1; JP6389905B2; EP3169029B1; EP3169029A4; WO2016006890A1

Abstract

Disclosed are a method and apparatus for transmitting and receiving data in a wireless communication system. Specifically, a method of transceiving data by a terminal in an unlicensed band of a wireless communication system may include the steps of: performing blind detection for detecting a predetermined signal transmitted from a base station at a cell in an unlicensed band; and determining a period for detecting the signal via blind detection as a Reserved Resource Period (RRP), which is a period of time that has been reserved for transceiving data at a cell in the unlicensed band.

Description

Method and apparatus for transceiving data in wireless communication system

Technical Field

The present invention relates to a wireless communication system, and more particularly, to a method of transmitting and receiving data in an unlicensed band and an apparatus supporting the same.

Background

Mobile communication systems have been developed to provide voice services while ensuring user activities. However, the service coverage of the mobile communication system has been extended even to data services as well as voice services. Nowadays, resource shortage is caused by explosive increase of services, and more advanced mobile communication systems are required due to user's demand for higher speed services.

Requirements of the next generation mobile communication system include support of huge data traffic, significant increase in transfer rate per user, accommodation of significantly increased number of connected devices, very low end-to-end delay, and high energy efficiency. To this end, various technologies such as dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, non-orthogonal multiple access (NOMA), support for ultra-wideband, and device networking are being investigated.

Disclosure of Invention

Technical problem

In 3GPP, since mobile communication data traffic is explosively increasing, services in an unlicensed band/spectrum have been suggested as one of schemes for satisfying the rapid growth of mobile communication data traffic. In this case, in order to transmit and receive data in an unlicensed band/spectrum, it is necessary to minimize an influence on other communication systems (e.g., 802.11 systems) and occupy a corresponding band via contention, but such a method has not been defined yet.

Embodiments of the present invention propose methods of transmitting and receiving data between a UE and an eNB in an unlicensed band/spectrum.

Further, an embodiment of the present invention proposes a method for determining a period of time during which radio resources have been occupied in order to transmit and receive data by performing blind detection on a specific signal in an unlicensed band/spectrum.

Furthermore, embodiments of the present invention propose a method of performing a restricted measurement operation by a UE in a time period occupied in an unlicensed band/spectrum.

The technical objects achieved by the present invention are not limited to the aforementioned objects, and other technical objects may be obviously understood by those skilled in the art to which the present invention pertains from the following description.

Technical scheme

In an aspect of the present invention, a method of transmitting and receiving data by a UE in an unlicensed band in a wireless communication system may include: blind detection for detecting a predetermined specific signal transmitted from the eNB is performed in the cell of the unlicensed band, and a period for detecting the signal via the blind detection is determined as a Reserved Resource Period (RRP), which is a period occupied by transmission and reception of data in the cell of the unlicensed band.

In another aspect of the present invention, a user equipment for transmitting and receiving data in an unlicensed band in a wireless communication system, includes: a Radio Frequency (RF) unit configured to transmit and receive a radio signal; and a processor configured to control the user equipment. The processor may perform blind detection for detecting a predetermined specific signal transmitted by the eNB in a cell of the unlicensed band, and may determine a period for detecting the signal via the blind detection as a Reserved Resource Period (RRP), which is a period occupied by transmission and reception of data in the cell of the unlicensed band.

The method may further include receiving RRP configuration information including parameters for blind detection of Reference Signals (RSs) and/or for determining RRPs from the eNB.

The RRP configuration information may include one or more of a sequence scrambling initialization parameter of the signal, information for identifying a radio frame boundary in a cell of the unlicensed band, information on a transmission bandwidth of the signal, information on a power level threshold for RRP determination, a number of antenna ports in which the signal is transmitted, a Multicast Broadcast Single Frequency Network (MBSFN) subframe configuration, a QCL-capable assumed reference signal, and a large-scale (large-scale) characteristic of a wireless channel.

If the power level threshold is set in a subframe unit, a subframe in which an average reception power value of resource elements in which signals are transmitted is greater than or equal to the power level threshold may be determined to belong to the RRP.

If a power level threshold is set in an Orthogonal Frequency Division Multiplexing (OFDM) symbol unit, a subframe in which the number of OFDM symbols in which an average reception power value of resource elements in which a signal is transmitted is greater than or equal to the power level threshold is greater than or equal to a certain number may be determined to belong to an RRP.

The QCL-capable reference signals may include reference signals transmitted in a cell of a licensed band.

The Doppler shift value of the cell of the unlicensed band may be derived by correcting a Doppler shift (Doppler shift) estimation value estimated from a reference signal transmitted in the cell of the licensed band based on a ratio between a center frequency of the cell of the licensed band and a center frequency of the cell of the unlicensed band.

The boundary of the floating radio frame may be determined from a time point of detecting a signal or after a certain time from the time point of detecting a signal with respect to a cell of the unlicensed band.

The radio frame number of the cell of the unlicensed band may be sequentially increased at the same interval as that of the radio frame of the licensed band from the boundary of the floating radio frame regardless of the radio frame number of the cell of the licensed band.

The blind detection operation may be stopped for a certain time from a point of time when the boundary of the floating radio frame is obtained by blind detection.

If both the cell of the unlicensed band and the cell of the licensed band support hybrid automatic repeat request (HARQ) operation, a timeline of HARQ may be determined based on radio frame boundaries of the cell of the licensed band.

A power increase may be applied to a signal transmitted in the first subframe of the RRP.

The method may further comprise: by the UE, measurement is performed using a reference signal transmitted from the eNB in a measurement object limited within the RRP.

The restricted measurement object may be set by the eNB or determined within the RRP as a subframe in which the average received power of the reference signal is greater than or equal to a certain threshold.

If the RRP is a discontinuous period of time, the restricted measurement object may be determined as a subframe in which the average received power of the reference signal is greater than or equal to a certain threshold within the RRP within a certain time window.

Advantageous effects

According to embodiments of the present invention, data may be transmitted and received in an unlicensed band/spectrum while minimizing impact on other wireless communication systems.

Furthermore, according to embodiments of the present invention, the time period in which the radio resources have been occupied can be flexibly determined, and signaling related to the time period in which the radio resources have been occupied can be minimized because the UE determines the time period in which the radio resources have been occupied in the unlicensed band/spectrum.

Furthermore, according to the embodiments of the present invention, even in an unlicensed band/spectrum, a restricted measurement operation for a UE can be smoothly supported.

The advantages that can be obtained by the present invention are not limited to the aforementioned advantages, and various other advantages can be clearly understood by those skilled in the art to which the present invention pertains from the following description.

Drawings

The accompanying drawings, which are included as part of the specification to assist in understanding the invention, provide embodiments of the invention, and describe technical features of the invention by way of the following description.

Fig. 1 illustrates a structure of a radio frame in a wireless communication system to which an embodiment of the present invention can be applied.

Fig. 2 is a diagram illustrating a resource grid for a downlink slot in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 3 illustrates a structure of a downlink subframe in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 4 illustrates a structure of an uplink subframe in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 5 shows a configuration of a known MIMO communication system.

Fig. 6 is a diagram illustrating channels from multiple transmit antennas to a single receive antenna.

Fig. 7 illustrates an example of component carriers and carrier aggregation in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 8 illustrates an example of a structure of a subframe according to cross-carrier scheduling in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 9 is a diagram illustrating a time-frequency resource block in a time-frequency domain in a wireless communication system to which an embodiment of the present invention can be applied.

Fig. 10 is a diagram illustrating resource allocation and retransmission processes of an asynchronous HARQ method in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 11 is a diagram illustrating a downlink HARQ process in an LTE FDD system to which an embodiment of the present invention may be applied.

Fig. 12 is a diagram illustrating an uplink HARQ process in an LTE FDD system to which an embodiment of the present invention can be applied.

Fig. 13 is a diagram illustrating a carrier aggregation-based CoMP system in a wireless communication system to which an embodiment of the present invention can be applied.

Fig. 14 illustrates a reference signal pattern mapped to a downlink resource block pair in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 15 is a diagram illustrating a PDCCH and an E-PDCCH in a wireless communication system to which an embodiment of the present invention may be applied.

Fig. 16 is a diagram illustrating carrier aggregation in an unlicensed band/spectrum according to an embodiment of the present invention.

Fig. 17 to 19 are diagrams illustrating a method of transmitting and receiving data in an unlicensed band/spectrum according to an embodiment of the present invention.

Fig. 20 and 21 are diagrams illustrating floating radio frame boundaries according to embodiments of the present invention.

Fig. 22 is a diagram illustrating a method of transmitting and receiving data in an unlicensed band/spectrum according to an embodiment of the present invention.

Fig. 23 illustrates a block diagram of a wireless communication device according to an embodiment of the present invention.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description to be disclosed hereinafter together with the accompanying drawings is intended to describe embodiments of the present invention, and not to describe the only embodiments for carrying out the present invention. The following detailed description includes details in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without the specific details.

In some cases, in order to prevent the concept of the present invention from being ambiguous, known structures and devices may be omitted, or may be illustrated in a block diagram format based on the core function of each structure and device.

In the specification, a base station means a terminal node of a network that directly performs communication with a terminal. In this document, a specific operation described as being performed by the base station may be performed by an upper node of the base station in some cases. That is, it is apparent that, in a network configured by a plurality of network nodes including a base station, various operations performed for communication with a terminal may be performed by the base station or other network nodes other than the base station. A Base Station (BS) may be generally replaced with terms such as a fixed station, a node B, an evolved nodeb (enb), a Base Transceiver System (BTS), an Access Point (AP), and the like. In addition, a "terminal" may be fixed or movable and is replaced with terms such as User Equipment (UE), a Mobile Station (MS), a User Terminal (UT), a mobile subscriber station (MSs), a Subscriber Station (SS), an Advanced Mobile Station (AMS), a Wireless Terminal (WT), a Machine Type Communication (MTC) device, a machine to machine (M2M) device, a device to device (D2D) device, and the like.

Hereinafter, downlink means communication from a base station to a terminal, and uplink means communication from a terminal to a base station. In the downlink, the transmitter may be part of a base station and the receiver may be part of a terminal. In the uplink, the transmitter may be part of a terminal and the receiver may be part of a base station.

Specific terms used in the following description are provided to help understanding of the present invention, and the use of the specific terms may be modified into other forms within a scope not departing from the technical spirit of the present invention.

The following techniques may be used in various wireless access systems such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), single carrier-FDMA (SC-FDMA), non-orthogonal multiple access (NOMA), and the like. CDMA may be implemented by a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA 2000. TDMA may be implemented by a radio technology such as global system for mobile communications (GSM)/General Packet Radio Service (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11(Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, E-UTRA (evolved UTRA), and so on. UTRA is part of the Universal Mobile Telecommunications System (UMTS). Third generation partnership project (3GPP) Long Term Evolution (LTE), which is part of evolved UMTS (E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), employs OFDMA in the downlink and SC-FDMA in the uplink. LTE-advanced (LTE-a) is an evolution of 3GPP LTE.

Embodiments of the present invention may be based on standard documents disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 as a wireless access system. That is, steps or portions, which are not described to clearly show the technical spirit of the present invention among the embodiments of the present invention, may be based on these documents. In addition, all terms disclosed in this document may be described by a standard document.

For clarity of description, the 3GPP LTE/LTE-a is mainly described, but the technical features of the present invention are not limited thereto.

Conventional systems to which embodiments of the present invention may be applied

The 3GPP LTE/LTE-a supports a radio frame structure type 1 applicable to Frequency Division Duplexing (FDD) and a radio frame structure applicable to Time Division Duplexing (TDD).

In fig. 1, the size of a radio frame in the time domain is represented as T _ s being a multiple of a time unit of 1/(15000 × 2048). Downlink and uplink transmissions include radio frames with a periodicity of T _ f 307200T _ s 10 ms.

Fig. 1(a) illustrates the structure of a type 1 radio frame. Type 1 radio frames may be applicable to both full duplex and half duplex FDD.

The radio frame includes 10 subframes. A radio frame consists of 20 slots of length T _ slot 15360T _ s 0.5 ms. Indexes 0 to 19 are allocated to the corresponding slots. One subframe includes 2 slots that are consecutive in the time domain, and subframe i includes slot 2i and slot 2i + 1. The time taken to transmit one subframe is referred to as a transmission time period (TTI). For example, the length of one subframe may be 1ms, and the length of one slot may be 0.5 ms.

In FDD, uplink transmission and downlink transmission are divided in the frequency domain. There is no limitation on full duplex FDD, whereas in half duplex FDD operation the UE cannot transmit and receive data simultaneously.

One slot includes a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a time domain and a plurality of Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, an OFDM symbol is used to represent one symbol period because OFDMA is used in downlink. One OFDM symbol may be referred to as one SC-FDMA symbol or symbol period. The RB is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot.

Fig. 1(b) shows a frame structure type 2.

Frame structure type 2 includes two half-frames each having a length of 153600 × T _ s — 5 ms. Each field includes 5 subframes, each having a length of 30720 × T _ s — 1 ms.

In frame structure type 2 of the TDD system, an uplink-downlink configuration is a rule indicating whether or not uplink and downlink are allocated (or reserved) to all subframes. Table 1 shows an uplink-downlink configuration.

[ Table 1]

Referring to table 1, in each subframe of a radio frame, "D" denotes a subframe for downlink transmission, "U" denotes a subframe for uplink transmission, and "S" denotes a special subframe including three type fields including a downlink pilot time slot (DwPTS), a Guard Period (GP), and an uplink pilot time slot (UpPTS).

The DwPTS is used in the UE for initial cell search, synchronization, or channel estimation. UpPTS is used in eNB for synchronization and channel estimation of uplink transmission of UE. The GP is a period for removing interference generated in the uplink due to a multipath delay of a downlink signal between the uplink and the downlink.

Each subframe i comprises a slot 2i and a slot 2i +1, each having a length T _ slot 15360 × T _ s 0.5 ms.

The uplink-downlink configuration can be divided into 7 types. The positions and/or numbers of downlink subframes, special subframes, and uplink subframes are different in each configuration.

A point of time at which a change is performed from downlink to uplink, or a point of time at which a change is performed from uplink to downlink is referred to as a switching point. The period of the switching point means that the period in which the uplink subframe and the downlink subframe are changed is equally repeated. Both 5ms and 10ms are supported in the period of the switching point. If the switching point periodicity has a 5ms downlink-uplink switching point periodicity, then a special subframe S is present in each half-frame. If the switching point periodicity has a 10ms downlink-uplink switching point periodicity, the special subframe S is present only in the first half frame.

In all configurations, 0 and 5 subframes and DwPTS are used for downlink transmission only. The UpPTS and the subframe following the subframe are always used for uplink transmission.

Such uplink-downlink configuration may be known to both the eNB and the UE as system information. The eNB may inform the UE of a change in uplink-downlink allocation status of a radio frame by transmitting only an index of uplink-downlink configuration information to the UE whenever the uplink-downlink configuration information is changed. Further, the configuration information is a downlink control information type and may be transmitted via a Physical Downlink Control Channel (PDCCH) like other scheduling information. The configuration information may be transmitted as broadcast information to all UEs within the cell via a broadcast channel.

Table 2 shows the configuration of the special subframe (length of DwPTS/GP/UpPTS).

[ Table 2]

The structure of the radio frame according to the example of fig. 1 is only an example. The number of subcarriers included in a radio frame or the number of slots included in a subframe and the number of OFDM symbols included in a slot may be varied in various ways.

Fig. 2 is a diagram illustrating a resource grid of one downlink slot in a wireless communication system to which an embodiment of the present invention can be applied.

Referring to fig. 2, one downlink slot includes a plurality of OFDM symbols in the time domain. Herein, it is exemplarily described that one downlink slot includes 7 OFDM symbols and one resource block includes 12 subcarriers in the frequency domain, but the present invention is not limited thereto.

Each element on the resource grid is referred to as a resource element, and one resource block includes 12 × 7 resource elements. The number NDL of resource blocks included in a downlink slot depends on the downlink transmission bandwidth.

The structure of the uplink slot may be the same as that of the downlink slot.

Fig. 3 illustrates a structure of a downlink subframe in a wireless communication system to which an embodiment of the present invention can be applied.

Referring to fig. 3, a maximum of the first three OFDM symbols in the first slot of the subframe are a control region allocated with a control channel, and the remaining OFDM symbols are a data region allocated with a Physical Downlink Shared Channel (PDSCH). Examples of the downlink control channel used in the 3GPP LTE include a Physical Control Format Indicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), and the like.

The PFCICH is transmitted in the first OFDM symbol of the subframe and transmits information on the number of OFDM symbols for transmitting the control channel in the subframe (i.e., the size of the control region). The PHICH is a response channel of an uplink and carries an Acknowledgement (ACK)/negative-acknowledgement (NACK) signal for hybrid automatic repeat request (HARQ). Control information transmitted through the PDCCH is referred to as Downlink Control Information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information, or an uplink transmit (Tx) power control command for a specific terminal group.

The PDCCH may carry resource allocation and transport format (also referred to as a downlink grant) of a downlink shared channel (DL-SCH), resource allocation information (also referred to as an uplink grant) of an uplink shared channel (UL-SCH), paging information in a Paging Channel (PCH), system information in the DL-SCH, resource allocation of an upper layer control message such as a random access response transmitted in the PDSCH, a set of transmission power control commands for individual terminals in a specific terminal group, activation of voice over IP (VoIP), and the like. A plurality of PDCCHs may be transmitted in the control region and the terminal may monitor the plurality of PDCCHs. The PDCCH is transmitted on a single Control Channel Element (CCE) or on an aggregation of some consecutive CCEs. The CCE is a logical allocation unit used to provide the PDCCH with a coding rate according to a state of a radio channel. CCEs correspond to a plurality of resource element groups. The format of the PDCCH and the number of bits of the available PDCCH are determined according to the association relationship between the number of CCEs and the coding rate provided by the CCEs.

The base station determines a PDCCH format according to DCI to be transmitted to the UE, and attaches a Cyclic Redundancy Check (CRC) to the control information. A unique identifier (radio network temporary identifier (RNTI)) is masked to the CRC according to the owner or usage of the PDCCH. If the PDCCH is a PDCCH for a specific terminal, a unique identifier of the terminal, for example, cell-RNTI (C-RNTI), may be masked to the CRC. If the PDCCH is a PDCCH for a paging message, a paging indicator identifier (e.g., paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is a PDCCH for system information, more particularly, a System Information Block (SIB), a system information identifier (e.g., System Information (SI) -RNTI) may be masked to the CRC. A Random Access (RA) -RNTI may be masked to the CRC to indicate a random access response that is a response to transmission of a random access preamble of the UE.

Fig. 4 illustrates a structure of an uplink subframe in a wireless communication system to which an embodiment of the present invention can be applied.

Referring to fig. 4, an uplink subframe may be divided into a control region and a data region in a frequency domain. A Physical Uplink Control Channel (PUCCH) transmitting uplink control information is allocated to the control region. A Physical Uplink Shared Channel (PUSCH) for transmitting user data is allocated to the data region. One terminal does not transmit PUCCH and PUSCH at the same time in order to maintain a single carrier characteristic.

In a subframe, Resource Block (RB) pairs are allocated to a PUCCH for one UE. Including RBs belonging to an RB pair, occupy different subcarriers in each of two slots. This is called that the RB pair allocated to the PUCCH hops at the slot boundary.

Multiple Input Multiple Output (MIMO)

The MIMO technology does not use a single transmit antenna and a single receive antenna, which have been generally used so far, but uses a plurality of transmit (Tx) antennas and a plurality of receive (Rx) antennas. In other words, the MIMO technology is a technology for improving capacity or enhancing performance using multiple input/output antennas in a transmitting end or a receiving end of a wireless communication system. Hereinafter, MIMO is referred to as "multiple input/output antenna".

More specifically, the multiple input/output antenna technique does not rely on a single antenna path in order to receive a single aggregate message and to complete aggregate data by collecting multiple data blocks received via several antennas. Accordingly, the multiple input/output antenna technology may increase a data transfer rate within a specific system range, and may also increase the system range via the specific data transfer rate.

It is expected that efficient multiple input/output antenna technology will be used because next generation mobile communication requires a higher data transfer rate than existing mobile communication. Under such circumstances, the MIMO communication technology is a next-generation mobile communication technology which can be widely used in mobile communication UEs and relay nodes, and has attracted public attention as a technology that can overcome a limitation on a transmission rate of another mobile communication due to the expansion of data communication.

Multiple input/output antenna (MIMO) technology, which is a variety of transmission efficiency improvement techniques being developed, has attracted considerable attention as a method capable of significantly improving communication capacity and transmission/reception performance even without additional frequency allocation or power increase.

Fig. 5 shows a configuration of a known MIMO communication system.

Referring to fig. 5, if the number of transmit (Tx) antennas is increased to N _ T and the number of receive (Rx) antennas is simultaneously increased to N _ R, a theoretical channel transmission capacity is increased in proportion to the number of antennas, unlike a case where a plurality of antennas are used only in a transmitter or a receiver. Therefore, the transmission rate can be increased, and the frequency efficiency can be significantly improved. In this case, the transmission rate according to the increase in the channel transmission capacity can be theoretically increased to a value obtained by multiplying the following rate increment R _ i by the maximum transmission rate R _ o when one antenna is used.

[ equation 1]

R_i＝min(N_T,N_R)

That is, for example, in a MIMO communication system using 4 transmission antennas and 4 reception antennas, a transmission rate of four times can be theoretically obtained as compared with a single antenna system.

Such multiple input/output antenna technology can be divided into a spatial diversity method for improving transmission reliability using symbols passing through various channel paths and a spatial multiplexing method for increasing a transmission rate by simultaneously transmitting a plurality of data symbols using a plurality of transmit antennas. Further, active research is recently being conducted on a method of appropriately obtaining the advantages of the two methods by combining the two methods.

Each of the methods will be described in more detail below.

First, the spatial diversity method includes a space-time block code series method and a space-time tresis code series method using both diversity gain and coding gain. Generally, the tress code series method is better in terms of bit error rate improvement performance and code generation freedom, while the space-time block code series method has low operation complexity. Such a spatial diversity gain may correspond to an amount corresponding to a product (N _ T × N _ R) of the number of transmit antennas (N _ T) and the number of receive antennas (N _ R).

Second, the spatial multiplexing scheme is a method for transmitting different data streams in the transmit antennas. In this case, in the receiver, mutual interference is generated between data simultaneously transmitted by the transmitter. The receiver removes interference using an appropriate signal processing scheme and receives the data. The noise removal methods used in this case may include a Maximum Likelihood Detection (MLD) receiver, a Zero Forcing (ZF) receiver, a Minimum Mean Square Error (MMSE) receiver, a diagonal bell labs layered space-time code (D-BLAST), and a vertical bell labs layered space-time code (V-BLAST). In particular, if the transmitting end can know channel information, a Singular Value Decomposition (SVD) method may be used.

Third, there is a method using a combination of spatial diversity and spatial multiplexing. If only a spatial diversity gain is to be obtained, the performance improvement gain according to an increase in diversity difference gradually saturates. If only the spatial multiplexing gain is used, transmission reliability in a radio channel is deteriorated. Methods for solving this problem and obtaining two gains have been studied, and may include a double space-time transmit diversity (double STTD) method and space-time bit interleaved coded modulation (STBICM).

To describe the communication method in the multiple input/output antenna system, such as described above, in more detail, the communication method may be represented as follows via a mathematical model.

First, as shown in fig. 5, it is assumed that there are N _ T transmit antennas and N _ R receive antennas.

First, a transmission signal is described below. If there are N _ T transmit antennas as described above, the maximum number of information units that can be transmitted is N _ T, which can be represented using the following vector.

[ equation 2]

The transmission power may be different in each of the transmission information units s _1, s _ 2. In this case, if the unit of transmission power is P _1, P _2,.. or P _ NT, the transmission information having the controlled transmission power may be represented using the following vector.

[ equation 3]

In equation 3, transmission information having controlled transmission power may be represented as follows using a diagonal matrix P of transmission power.

[ equation 4]

The information vector with the controlled transmission power is multiplied by the weighting matrix W in equation 4, thus forming the N _ T transmission signals x _1, x _2,. -, x _ NT actually transmitted. In this case, the weighting matrix functions to appropriately allocate transmission information to the antennas according to the transmission channel conditions. The following may be denoted using transmission signals x _1, x _2,. -, x _ NT.

[ equation 5]

In equation 5, W _ ij represents a weight between the ith transmission antenna and the jth transmission information, and W is a representation of a matrix of weights. Such a matrix W is called a weighting matrix or a precoding matrix.

A transmission signal x such as described above can be considered for use in situations where spatial diversity is used and in situations where spatial multiplexing is used.

If spatial multiplexing is used, all elements of the information vector s have different values because different signals are multiplexed and transmitted. In contrast, if spatial diversity is used, elements of all information vectors s have the same value because the same signal is transmitted via several channel paths.

A method of mixing spatial multiplexing and spatial diversity may be considered. In other words, for example, the same signal may be transmitted using spatial diversity via 3 transmit antennas, and the remaining different signals may be spatially multiplexed and transmitted.

If there are N _ R receive antennas, the receive signals y _1, y _2,. and y _ NR of the respective antennas are represented as follows using a vector y.

[ equation 6]

Meanwhile, if a channel is simulated in a multiple input/output antenna communication system, the channel may be divided by a transmission/reception antenna index. The channel flowing from the transmit antenna j through the receive antenna i is denoted h _ ij. In this case, it should be noted that the index of the receiving antenna first appears and the index of the transmitting antenna then appears in the order of the index of h _ ij.

Several channels may be grouped and represented in vector and matrix form. For example, the vector representation is described below.

Fig. 6 is a schematic diagram showing channels from multiple transmit antennas to a single receive antenna.

As shown in fig. 6, channels from a total of N _ T transmit antennas to a receive antenna i may be represented as follows.

[ equation 7]

Further, if all channels from N _ T transmit antennas to N _ R receive antennas are represented via a matrix, such as equation 7, they may be represented as follows.

[ equation 8]

After the actual channel experiences the channel matrix H, Additive White Gaussian Noise (AWGN) is added to the actual channel. Therefore, AWGN N _1, N _2,. and N _ NR added to N _ R receiving antennas are represented by the following vectors, respectively.

[ equation 9]

The transmission signal, the reception signal, the channel, and the AWGN in the multiple input/output antenna communication system may be represented by modeling such as the transmission signal, the reception signal, the channel, and the AWGN as described above as having the following relationships.

[ equation 10]

The number of rows and columns of the channel matrix H indicating the channel state is determined by the number of transmit/receive antennas. In the channel matrix H, as described above, the number of rows becomes equal to the number of reception antennas N _ R, and the number of columns becomes equal to the number of transmission antennas N _ T. That is, the channel matrix H becomes an N _ R × N _ T matrix.

In general, the rank of a matrix is defined as the minimum number of independent rows or columns. Thus, the rank of the matrix is not greater than the number of rows or columns. In a symbolic form, for example, the rank H of the channel matrix H is defined as follows.

[ equation 11]

rank(H)≤min(N_T,N_R)

Further, if the matrix undergoes eigenvalue decomposition, the rank may be defined as the number of eigenvalues, which belong to the eigenvalues, and are not 0. Likewise, if a rank is subjected to Singular Value Decomposition (SVD), it may be defined as the number of singular values other than 0. Thus, the physical meaning of rank in a channel matrix can be said to be the maximum number of different information that can be sent over it in a given channel.

In this specification, a "rank" for MIMO transmission indicates the number of paths via which signals can be independently transmitted on a specific time point and a specific frequency resource. The "number of layers" indicates the number of signal streams transmitted via each path. Generally, unless otherwise described, a rank has the same meaning as the number of layers, because a transmission end transmits the number of layers corresponding to the number of ranks used in signal transmission.

Generic carrier aggregation

The communication environment considered in the embodiments of the present invention includes a multicarrier support environment. That is, the multi-carrier system or the carrier aggregation system used in the present invention means a system that aggregates and uses one or more Component Carriers (CCs) having a smaller bandwidth than a target band when configuring a target wideband so as to support the wideband.

In the embodiment of the present invention, multicarrier means aggregation of carriers (alternatively, carrier aggregation), and in this case, aggregation of carriers means both aggregation between consecutive carriers and aggregation between non-consecutive carriers. In addition, the number of component carriers aggregated between downlink and uplink may be set differently. A case where the number of downlink component carriers (hereinafter, referred to as "DL CCs") and the number of uplink component carriers (hereinafter, referred to as "UL CCs") are identical to each other is referred to as symmetric aggregation, and a case where the number of downlink component carriers and the number of uplink component carriers are different from each other is referred to as asymmetric aggregation. Carrier aggregation may be used in combination with terms such as carrier aggregation, bandwidth aggregation, spectrum aggregation, and the like.

Carrier aggregation configured by combining two or more component carriers is intended to support bandwidths up to 100MHz in an LTE-a system. When one or more carriers having bandwidths other than the target frequency band are combined, the bandwidths of the carriers to be combined may be limited to the bandwidths used in the existing system in order to maintain backward compatibility with the existing IMT system. For example, the existing 3GPP LTE system supports bandwidths of 1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz, and 20MHz, and the 3GPP LTE-advanced system (i.e., LTE-a) may be configured to support bandwidths greater than 20MHz by using on the bandwidth so as to be compatible with the existing system. In addition, the carrier aggregation system used in the present invention may be configured to support carrier aggregation by defining a new bandwidth independently of a bandwidth used in an existing system.

The LTE-a system uses the concept of a cell in order to manage radio resources.

The aforementioned carrier aggregation environment may be referred to as a multi-cell environment. A cell is defined as a combination of a pair of downlink resources (DL CCs) and uplink resources (UL CCs), but the uplink resources are not essential elements. Thus, a cell may be composed of only downlink resources or both downlink and uplink resources. A specific terminal may have one DL CC and one UL CC if the cell has only one configured serving cell, as many DL CCs as the cell if the cell has two or more configured serving cells, and the number of UL CCs may be equal to or less than the number of DL CCs.

In some embodiments, DL CCs and UL CCs may be configured in an opposite manner. That is, if a specific terminal has a plurality of configured serving cells, a carrier aggregation environment having more UL CCs than DL CCs may also be supported. That is, carrier aggregation may be considered as aggregation of two or more cells having different carrier frequencies (center frequencies). In this case, the "cell" should be distinguished from the "cells" of the area normally covered by the base station.

Cells used in the LTE-a system include a primary cell (PCell) and a secondary cell (SCell). The PCell and SCell may be used as serving cells. In case of a UE in an RRC _ CONNECTED state but not configured with carrier aggregation or not supporting carrier aggregation, there is only one serving cell configured as a PCell only. In contrast, in a terminal that is in an RRC _ CONNECTED state and is not configured with carrier aggregation, one or more serving cells may exist, and a PCell and one or more scells are included in all the serving cells.

The serving cells (PCell and SCell) may be configured by RRC parameters. The physcellld, which is the physical layer identifier of a cell, has an integer value of 0 to 503. Scelllindex, which is a short identifier used to identify an SCell, has an integer value of 1 to 7. The ServCellIndex, which is a short identifier used to identify a serving cell (PCell or SCell), has an integer value of 0 to 7. The value 0 is applied to PCell and scelllindex is pre-allocated for application to scell. That is, in terms of ServCellIndex, a cell having the smallest cell ID (alternatively, cell index) becomes PCell.

PCell means a cell operating on a primary frequency (alternatively, a primary CC). The PCell may be used for the UE to perform an initial connection establishment procedure or a connection re-establishment procedure, and may refer to a cell indicated during a handover procedure. In addition, the PCell means a cell belonging to a serving cell configured in a carrier aggregation environment and becoming a center for controlling related communication. That is, the UE may receive an allocated PUCCH and transmit the PUCCH only in its PCell, and acquire system information or change a monitoring procedure using only the PCell. For a UE supporting a carrier aggregation environment, an evolved universal terrestrial radio access network (E-UTRAN) may change a PCell only for a handover procedure by using an RRC connection reconfiguration (rrcconnectionreconfiguration) message including mobility control information (mobility control info) of an upper layer.

An SCell means a cell operating on a secondary frequency (alternatively, a secondary CC). Only one PCell may be allocated to a specific terminal and one or more scells may be allocated to a specific UE. The SCell may be configured after RRC connection establishment is achieved and used to provide additional radio resources. PUCCH is not present in the remaining cells other than PCell (i.e., scells belonging to a serving cell configured in a carrier aggregation environment). The E-UTRAN may provide all types of system information related to the operation of the relevant cell in the RRC _ CONNECTED state through a dedicated signal when the SCell is added to the UE supporting the carrier aggregation environment. The change of system information may be controlled by releasing and adding the relevant SCell, and in this case, an RRC connection reconfiguration (rrcconnectionreconfiguration) message of an upper layer may be used. The E-UTRAN may perform dedicated signaling with different parameters for each UE instead of broadcasting in the relevant SCell.

After the initial security activation procedure is started, the E-UTRAN adds an SCell to a PCell initially configured during a connection establishment procedure to configure a network including one or more scells. In a carrier aggregation environment, the PCell and the SCell may operate as respective component carriers. In the embodiments described below, a Primary Component Carrier (PCC) may be used in the same meaning as a PCell, and a Secondary Component Carrier (SCC) may be used in the same meaning as an SCell.

Fig. 7 illustrates an example of component carriers and carrier aggregation in a wireless communication system to which an embodiment of the present invention can be applied.

Fig. 7 (a) illustrates a single carrier structure used in the LTE system. The CCs include DL CCs and UL CCs. One component carrier may have a frequency range of 20 MHz.

Fig. 7(b) illustrates a carrier aggregation structure used in the LTE system. Fig. 7(b) shows an example in which three component carriers having a frequency bandwidth of 20MHz are aggregated. Fig. 7 illustrates three DL CCs and three UL CCs, but the number of DL CCs and the number of UL CCs are not limited. In case of carrier aggregation, the UE may monitor three CCs simultaneously, receive downlink signals/data, and may transmit uplink signals/data.

If N DL CCs are managed in a particular cell, the network may allocate M (M ≦ N) DL CCs to the UE. In this case, the UE may monitor only M limited DL CCs and receive DL signals. In addition, the network can give priority to L (L ≦ M ≦ N) DL CCs to allocate the primary DL CC to the UE, and in this case, the UE needs to monitor the L DL CCs specifically. This method can be applied to uplink transmission in the same manner.

The link between the carrier frequency of the downlink resource (or, DL CC) and the carrier frequency of the uplink resource (or, ul CC) may be indicated by an upper layer message such as an RRC message or system information. For example, the combination of DL resources and UL resources may be configured by linkage defined by system information block type 2(SIB 2). Specifically, the linking may mean a mapping relationship between a DL CC transmitting a PDCCH carrying a UL grant and a UL CC using the UL grant, and mean a mapping relationship between a DL CC (or, UL CC) in which data of HARQ is transmitted and a UL CC (or, DL CC) in which an HARQ ACK/NACK signal is transmitted.

When one or more scells are configured in the UE, the network may activate or deactivate the configured scells. The PCell is always activated. The network activates or deactivates the SCell by sending an activation/deactivation MAC control element.

The activation/deactivation MAC control element has a fixed size and consists of a single octet including 7C fields and 1R field. The C field is configured for each SCell index (scelllindex) and indicates activation/deactivation of the SCell. When the value of the C field is set to "1", it indicates activation of an SCell having an index of the corresponding SCell. When the value of the C field is set to "0", it indicates deactivation of the SCell having the index of the corresponding SCell.

Further, the UE maintains a timer (sCellDeactivationTimer) for each configured SCell, and deactivates the associated SCell when the timer expires. The same initial timer value is applied to each instance of timer () and is configured by RRC signaling. When scells are added, or after handover, the initial SCell has been deactivated.

The UE performs the following operations for each configured SCell in each TTI.

-when the UE receives an activation/deactivation MAC control element that activates an SCell in a specific TTI (subframe n), the UE activates the SCell in a TTI (subframe n +8 or thereafter)) corresponding to a predetermined timing, and (re) starts a timer associated with the respective SCell. Activation of the SCell as a UE refers to the UE applying common SCell operations such as transmission of a Sounding Reference Signal (SRS) on the SCell, reporting of Channel Quality Indication (CQI)/Precoding Matrix Indication (PMI)/Rank Indication (RI)/Precoding Type Indication (PTI) for the SCell, PDCCH monitoring on the SCell, and PDCCH monitoring for the SCell.

-when the UE receives an activation/deactivation MAC control element deactivating an SCell in a specific TTI (subframe n), or when a timer associated with an activated SCell expires in a specific TTI (subframe n), the UE deactivates the SCell in a TTI (subframe n +8 or thereafter) corresponding to a predetermined timing, stops the timer of the corresponding SCell, and refreshes the entire HARQ buffer associated with the corresponding SCell.

-when the PDCCH of the serving cell associated with the scheduling activated SCell indicates an uplink grant or is used for downlink allocation, or when the PDCCH of the serving cell associated with the scheduling activated SCell indicates an uplink grant or is used for downlink allocation of the activated SCell, the UE restarts the timer associated with the corresponding SCell.

-when the SCell is deactivated, the UE does not send SRS about the SCell, does not report CQI/PMI/RI/PTI for the SCell, and does not send UL-SCH about the SCell, and does not monitor PDCCH about the SCell.

Cross-carrier scheduling

In a carrier aggregation system, two types of self-scheduling methods and cross-carrier scheduling methods are provided from the viewpoint of scheduling for a carrier or a serving cell. Cross-carrier scheduling may be referred to as cross-component carrier scheduling or cross-cell scheduling.

The cross-carrier scheduling means transmitting a PDCCH (DL grant) and a PDSCH to different corresponding DL CCs or transmitting a PUSCH transmitted according to a PDCCH (UL grant) transmitted in a DL CC on a different UL CC from a DL CC linked with the DL CC receiving the UL grant.

Whether cross-carrier scheduling is to be performed may be activated or deactivated in a UE-specific manner and semi-statically inform each UE through upper layer signaling (e.g., RRC signaling) whether cross-carrier scheduling is to be performed.

If cross-carrier scheduling is activated, a Carrier Indicator Field (CIF) through which DL/UL CC a notification of PDSCH/PUSCH indicated by a corresponding PDCCH is transmitted needs to be provided. For example, the PDCCH may allocate PDSCH resources or PUSCH resources to any one of a plurality of component carriers by using CIF. That is, if the PDCCH on the DL CC allocates PDSCH or PUSCH resources on one of a plurality of DL/UL CCs that have been aggregated, the CIF is set. In this case, the DCI format of LTE-a release 8 may be extended according to CIF. In this case, the set CIF may be fixed to a 3-bit field, and the position of the set CIF may be fixed regardless of the size of the DCI format. In addition, the PDCCH structure of LTE-a release 8 (same coding and same CCE based resource mapping) may be reused.

In contrast, if a PDCCH on a DL CC allocates a PDSCH resource on the same DL CC or allocates a PUSCH resource on one linked UL CC, the CIF is not set. In this case, the same PDCCH structure (same coding and same CCE based resource mapping) and DCI format as LTE-a release 8 may be used.

If cross-carrier scheduling is possible, the UE needs to monitor a PDCCH for a plurality of DCIs in a control region of a monitoring CC according to a transmission mode and/or bandwidth of each CC. Therefore, there is a need for a configuration and PDCCH monitoring that can support monitoring of a search space for a PDCCH for a plurality of DCIs.

In a carrier aggregation system, a UE DL CC set indicates a set of DL CCs for the UE that have been scheduled to receive PDSCH, and a UE UL CC set indicates a set of UL CCs for the UE that have been scheduled to transmit PUSCH. In addition, the PDCCH monitoring set indicates a set of at least one DL CC performing PDCCH monitoring. The PDCCH monitoring set may be the same as or a subset of the UE DL CC set. The PDCCH monitoring set may include at least any one of DL CCs in the UE DL CC set. Alternatively, the PDCCH monitoring set may be defined separately from the UE DL CC set. DL CCs included in the PDCCH monitoring set may be configured in such a way as to be always self-scheduled for linked UL CCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring set may be configured UE-specifically, UE group-specifically, or cell-specifically.

The deactivation of cross-carrier scheduling means that the PDCCH monitoring set is always the same as the UE DL CC set, if cross-carrier scheduling has been deactivated. And in this case no indication such as separate signaling for the PDCCH monitoring set is needed. However, if cross-carrier scheduling is activated, a PDCCH monitoring set may be defined in the UE DL CC set. That is, the base station transmits the PDCCH only through the PDCCH monitoring set in order to schedule the PDSCH or PUSCH for the UE.

Fig. 8 illustrates an example of a subframe structure according to cross-carrier scheduling in a wireless communication system to which an embodiment of the present invention can be applied.

Referring to fig. 8, three DL CCs are illustrated as being aggregated in a DL subframe for LTE-AUE. DL CC 'a' indicates a case of DL CC that has been configured as PDCCH monitoring DL CC. If CIF is not used, each DL CC may transmit a PDCCH scheduling its PDSCH without CIF. In contrast, if CIF is used through upper layer signaling, only one DL CC 'a' may transmit a PDCCH scheduling its PDSCH or a PDSCH of another CC by using CIF. In this case, DL CCs 'B' and 'C' which are not configured as PDCCH monitoring DL CCs do not transmit PDCCHs.

Hybrid automatic repeat request (HARQ)

In a mobile communication system, one eNB transmits and receives data to and from a plurality of UEs in one cell/sector via a wireless channel environment.

In a system in which a plurality of carriers operate, or a system operating in a form similar to the system, an eNB receives packet traffic via the wired internet and transmits the received packet traffic to a UE using a predetermined communication method. In this case, it is downlink scheduling, i.e., the eNB determines which frequency domain is used to transmit data to which UE at which timing.

Further, the eNB receives data from the UE using a predetermined communication method, demodulates the received data, and transmits packet traffic via the wired internet. It is uplink scheduling, i.e. the eNB determines which frequency band is used at which timing to allow which UE to transmit uplink data. Generally, a UE having a better channel status transmits and receives data using more time and more frequency resources.

Resources in a system operating on multiple carriers and a system operating in a form similar to the system may be basically divided into a time domain and a frequency domain. A resource may be defined as a resource block. A resource block includes a specific N number of subcarriers and a specific M number of subframes or a predetermined time unit. In this case, N and M may be 1.

In fig. 9, one block refers to one resource block, and one resource block uses several subcarriers as one axis and uses a predetermined time unit as another axis. In the downlink, the eNB schedules one or more resource blocks for the selected UE according to a predetermined scheduling rule and transmits data to the UE using the allocated resource blocks. In the uplink, the eNB schedules one or more resource blocks to the selected UE according to a predetermined scheduling rule, and the UE transmits data using the allocated resources in the uplink.

After the scheduling and data are transmitted, if a frame is lost or corrupted, the error control method includes a more advanced form of automatic repeat request (ARQ) method and a hybrid ARQ (harq) method.

Basically, in the ARQ method, after one frame is transmitted, the transmission side waits for an acknowledgement message (ACK). The receiving side transmits an acknowledgement message (ACK) only when the frame is successfully received. If an error is generated in the received frame, the receiving side again transmits a negative ack (nack) message and deletes information on the received frame having the error from the receiving-end buffer. When receiving the ACK signal, the transmission side transmits a subsequent frame. When receiving the NACK message, the transmitting side retransmits the corresponding frame.

Unlike in the ARQ method, in the HARQ method, if a received frame cannot be demodulated, the receiving end transmits a NACK message to the transmitting end, but stores the already received frame in a buffer during a specific time and combines the stored frame with the previously received frame when the corresponding frame is retransmitted, thereby improving the success rate of reception.

Recently, a HARQ method more effective than the basic ARQ method is widely used. Such HARQ methods include several types. The HARQ method may be basically divided into a synchronous HARQ and an asynchronous HARQ according to retransmission timing, and may be divided into a channel adaptive method and a channel non-adaptive method according to whether a channel state is incorporated into an amount of resources used at the time of retransmission.

In the synchronous HARQ method, when initial transmission fails, subsequent retransmission is performed by the system at a predetermined timing. That is, assuming that timing is performed every fourth time unit at the time of retransmission after initial transmission failure, the eNB and the UE need not additionally notify such timing because the timing has been agreed between the eNB and the UE. In this case, if the data transmission side has received the NACK message, it retransmits the frame every fourth time unit until it receives the ACK message.

In contrast, in the asynchronous HARQ method, retransmission timing may be rescheduled or may be performed via additional signaling. The timing when performing retransmissions for previously failed frames varies depending on several factors, such as channel conditions.

In the channel non-adaptive HARQ method, since they are already predetermined at the initial transmission, modulation of a frame, the number of resource blocks, and Adaptive Modulation and Coding (AMC) at the time of retransmission are performed. In contrast, in the channel adaptive HARQ method, modulation of a frame at the time of retransmission, the number of resource blocks, and Adaptive Modulation and Coding (AMC) are performed to vary according to the state of a channel. For example, in the channel non-adaptive HARQ method, the transmission side transmits data using 6 resource blocks at the initial transmission, and performs retransmission using 6 resource blocks in the same manner at the subsequent retransmission. In contrast, in the channel adaptive HARQ method, although transmission has been performed using 6 resource blocks, retransmission is then performed using resource blocks greater or smaller than 6 resource blocks according to a channel state.

Four HARQ combinations may be performed based on such classification, but the primarily used HARQ methods include asynchronous and channel adaptive HARQ methods and synchronous and channel non-adaptive HARQ methods.

The asynchronous and channel adaptive HARQ method can maximize retransmission efficiency because retransmission timing and the amount of used resources adaptively vary according to the state of a channel, but has a disadvantage of increased overhead. Therefore, asynchronous and channel adaptive HARQ methods are not considered to be commonly used for the uplink.

Synchronous and channel non-adaptive HARQ methods are beneficial where the overhead for timing of retransmissions and resource allocations is rarely present, since the timing for retransmissions and resource allocations is already predetermined within the system, but disadvantageously where retransmission efficiency is very low if such methods are used in severely changing channel conditions.

For example, in the case of downlink, ACK/NACK information is received from the UE after scheduling is performed and data is transmitted. A time delay is generated until the next data is transmitted as shown in fig. 10. Time delays are generated due to channel propagation delays and the time taken for data decoding and data encoding.

For such a delay period, a method of transmitting data using a separate HARQ process is used for data transmission without a blank. For example, if the shortest period between the next data transmission and the subsequent data transmission is 7 subframes, data may be transmitted without a blank if 7 independent processes are placed in 7 subframes.

The LTE physical layer supports HARQ in PDSCH and PUSCH and sends related acknowledgement of receipt (ACK) feedback in a separate control channel.

In the LTE FDD system, if the LTE FDD system does not operate in MIMO, 8 stop-and-wait (SAW) HARQ processes are supported in both uplink and downlink in a constant Round Trip Time (RTT) of 8 ms.

Fig. 11 is a diagram illustrating a downlink HARQ process in an LTE FDD system to which an embodiment of the present invention may be applied, and fig. 12 is a diagram illustrating an uplink HARQ process in an LTE FDD system to which an embodiment of the present invention may be applied.

Each HARQ process is defined by a unique HARQ process identifier (HARQ ID) of 3 bits size. The receiving end (i.e., UE in downlink HARQ process and enodeb in uplink HARQ process) needs a dedicated soft buffer allocation for the combination of retransmission data.

Also, for HARQ operation, New Data Indication (NDI), Redundancy Version (RV), and Modulation and Coding Scheme (MCS) fields are defined within the downlink control information. The NDI field toggles every time a new packet transmission is initiated. The RV field indicates an RV used for transmission or retransmission selection. The MCS field indicates an MCS level.

In LTE systems, the downlink HARQ process is an adaptive asynchronous method. Thus, the downlink control information for the HARQ process is explicitly concurrent with each downlink transmission.

In the LTE system, the uplink HARQ process is a synchronous method, and may include an adaptive or non-adaptive method. The uplink non-adaptive HARQ scheme requires a preset RV sequence (e.g., 0, 2, 3, 1, …) for continuous packet transmission because it does not occur simultaneously with explicit signaling of control information. In contrast, in the uplink adaptive HARQ scheme, the RV is explicitly signaled. In order to minimize control signaling, an uplink mode in which an RV (or MCS) is combined with another control information is also supported.

Constrained buffer rate matching (LBRM)

Complexity in UE implementation increases due to the overall memory needed to save Log Likelihood Ratios (LLRs) in order to support HARQ processes (throughout all HARQ processes), that is, UE HARQ soft buffer size.

The purpose of Limited Buffer Rate Matching (LBRM) is to maintain the peak data rate and minimize the impact on system performance and, in addition, reduce the UE HARQ soft buffer size. LBRM reduces the length of a virtual circular buffer for code block segmentation of Transport Blocks (TBs), which has a size larger than a predetermined size. With LBRM, the parent coding rate for the TB becomes a function of the UE soft buffer size, which is allocated to the TB size and TB. For example, for UE classes that do not support FDD operation, and UEs of the lowest class (e.g.,

UE classes

1 and 2 that do not support spatial multiplexing), the restriction on the buffer is transparent. That is, LBRM does not cause a reduction in soft buffer. In the case of high class UEs (i.e.,

UE classes

3, 4, and 5), the size of the soft buffer is calculated by assuming a 50% reduction in the buffer, which corresponds to two-halves of the mother coding rate for the eight HARQ processes and the maximum TB. Since the eNB knows the soft buffer capacity of the UE, the code bits are sent in a Virtual Circular Buffer (VCB), which may be stored in the HARQ soft buffer of the UE, for all given TB (re-) transmissions.

Coordinated multipoint transmission and reception (CoMP)

CoMP transmission is proposed to enhance the performance of the system, as per the requirements of LTE-advanced.

CoMP is referred to as a scheme for two or more enbs, and (access) points or cells interwork with each other and communicate with UEs in order to smoothly perform communication between a specific UE and an eNB (access) point or cell. CoMP is also known as cooperative MIMO, network MIMO, and the like. It is expected that CoMP will improve the performance of UEs located on the cell edge and increase the average throughput of the cell (sector).

In this specification, eNB, access point, and cell are used as the same meaning.

In general, inter-cell interference deteriorates performance of UEs located at a cell edge, and average cell (or sector) efficiency in a multi-cell environment where a frequency reuse factor is 1. To reduce inter-cell interference, simple passive methods such as Fractional Frequency Reuse (FFR) have been applied to LTE systems so that UEs located at the cell edge have appropriate performance efficiency in interference limited environments. However, instead of reducing the use of frequency resources for each cell, it is more beneficial to reuse inter-cell interference as a signal that the UE needs to receive or reduce inter-cell interference. In order to achieve the above-described object, a CoMP transmission method may be used.

The downlink-applicable CoMP method may be divided into a Joint Processing (JP) method and a coordinated scheduling/beamforming (CS/CB) method.

In the case of the JP method, data advancing from each eNB performing CoMP to the UE is instantaneously and simultaneously transmitted to the UE, and the UE combines signals from each of the enbs in order to improve reception performance. Meanwhile, in case of CS/CB, data advancing to the UE is instantaneously transmitted via a single eNB, and scheduling or beamforming is performed such that interference exerted by the UE on another eNB becomes minimum.

In the JP method, data may be used in each point (i.e., eNB) of the CoMP unit. The CoMP unit refers to a group of enbs used in the CoMP method. The JP method can be subdivided into a joint transmission method and a dynamic cell selection method.

The joint transmission method is a method of simultaneously transmitting signals via the PDSCH by a plurality of points, that is, some or all of the points of the CoMP unit. That is, data transmitted to one UE is simultaneously transmitted from a plurality of transmission points. The signal quality sent to a UE may be improved coherently or non-coherently, and interference between the UE and another UE may be actively removed via such a joint transmission method.

The dynamic cell selection method is a method in which a signal is transmitted via the PDSCH from one point of the CoMP unit. That is, data transmitted to one UE at a specific time is transmitted from one point, but is not transmitted to the UE from another point within the CoMP unit. The point at which data is transmitted to the UE may be dynamically selected.

According to the CS/CB method, the CoMP units cooperatively perform beamforming to transmit data to a UE. That is, data is transmitted only to the UE in the serving cell, but the scheduled/beamformed user may be determined via cooperation between multiple cells within the CoMP unit.

In some embodiments, CoMP reception refers to reception of signals transmitted through coordination between geographically separated points. The CoMP method applicable to the uplink may be divided into a Joint Reception (JR) method and a coordinated scheduling/beamforming (CS/CB) method.

The JR method is a method of receiving a signal transmitted via the PDSCH by a plurality of points, that is, some or all of the points of the CoMP unit. In the CS/CB method, a signal transmitted via the PDSCH is received only at one point, but user scheduling/beamforming may be determined via cooperation between a plurality of cells within the CoMP unit.

CA-based CoMP operation

In systems after LTE, coordinated multipoint (CoMP) transmission may be implemented using Carrier Aggregation (CA) functionality in LTE.

Fig. 13 illustrates that a primary cell (PCell) carrier and a secondary cell (SCell) carrier use the same frequency band on a frequency axis and are respectively allocated to two enbs which are geographically spaced apart from each other.

The serving eNB allocates a PCell to the UE1 and the neighboring eNB providing more interference allocates scells so that various DL/UL CoMP operations can be performed, such as JT, CS/CB and dynamic cell selection.

Fig. 13 shows an example in which a UE aggregates two enbs into a PCell and an SCell, respectively. In fact, the UE may aggregate three or more cells, and may perform CoMP operations with respect to some of the three cells in the same frequency band, and may perform simple CA operations with respect to other cells in different frequency bands. In this case, the PCell does not need to participate in the CoMP operation.

Reference Signal (RS)

In a wireless communication system, since data is transmitted via a radio channel, the signal may be distorted during transmission. In order for the receiver side to accurately receive the distorted signal, the distortion of the received signal needs to be corrected by using the channel information. In order to detect the channel information, a signal transmission method known to both the transmitter side and the receiver side and a method for detecting the channel information by using a distortion degree when the signal is transmitted through a channel are mainly used. The aforementioned signals are referred to as pilot signals or Reference Signals (RSs).

Recently, when packets are transmitted in most mobile communication systems, a plurality of transmission antennas and a plurality of reception antennas are employed to improve transmission/reception efficiency instead of a single transmission antenna and a single reception antenna. When data is transmitted and received by using the MIMO antenna, a channel state between the transmission antenna and the reception antenna needs to be detected in order to accurately receive the signal. Therefore, the respective transmit antennas need to have separate reference signals.

Reference signals in a wireless communication system can be largely classified into two types. In particular, there are reference signals for the purpose of channel information acquisition and reference signals for data demodulation. Since the purpose of the former reference signal is to allow a User Equipment (UE) to obtain channel information in Downlink (DL), the former reference signal will be transmitted over a wide band. And, even if the UE does not receive DL data in a specific subframe, it will perform channel measurement by receiving a corresponding reference signal. In addition, the corresponding reference signal may be used for measurement of mobility management of handover and the like. The latter reference signal is a reference signal transmitted together when the eNB transmits DL data. The UE may perform channel estimation if the UE receives a corresponding reference signal, thereby demodulating data. And, a corresponding reference signal will be transmitted in the data transmission region.

5 types of downlink reference signals are defined.

-cell specific reference signals (CRS)

Multicast-broadcast Single frequency network reference Signal (MBSFN RS)

-UE-specific reference signals or demodulation reference signals (DM-RS)

-Positioning Reference Signals (PRS)

-channel state information reference signal (CSI-RS)

One RS is transmitted in each downlink antenna port.

The CRS is transmitted in all downlink subframes in a cell supporting PDSCH transmission. The CRS is transmitted in one or more antenna ports 0-3. CRS is transmitted only in Δ f-15 kHz.

The MBSFN RS are transmitted in the MBSFN area of the MBSFN subframe only when the Physical Multicast Channel (PMCH) is transmitted. The MBSFN RS is transmitted in antenna port 4. MBSFN RSs are defined only in extended CP.

DM-RS supports transmission for PDSCH and is transmitted in antenna port p-5, p-7, p-8 or p-7, 8. In this case, ν is the number of layers used for PDSCH transmission. The DM-RS exists and is valid for demodulation of PDSCH only when PDSCH transmissions are correlated in the corresponding antenna port. The DM-RS is transmitted only in Resource Blocks (RBs) to which the corresponding PDSCH is mapped.

If any one of the physical channels or physical signals other than the DM-RS is transmitted using the Resource Elements (REs) of the same index pair (k, l) as the REs in which the DM-RS is transmitted, regardless of the antenna port "p", the DM-RS is not transmitted in the REs of the corresponding index pair (k, l).

PRSs are transmitted only in resource blocks within a downlink subframe configured for PRS transmission.

If both the generic subframe and the MBSFN subframe are configured as positioning subframes within one cell, the OFDM symbols within the MBSFN subframe configured for PRS transmission use the same CP as subframe # 0. If only MBSFN subframes are configured as positioning subframes within one cell, OFDM symbols configured for PRS within the MBSFN area of the respective subframe use an extended CP.

A start of an OFDM symbol configured for PRS transmission within a subframe configured for PRS transmission is the same as a start of a subframe in which all OFDM symbols have the same CP length as the OFDM symbol configured for PRS transmission.

The PRS are transmitted in antenna port 6.

Irrespective of the antenna port "p", PRS are not mapped to RE (k, l) allocated to Physical Broadcast Channel (PBCH), PSS, or SSS.

PRS are defined only in Δ f-15 kHz.

The CSI-RS is transmitted in 1, 2, 4 or 8 antenna ports using p 15, 16, p 15, a.18 and p 15, a.22, respectively.

CSI-RS is defined only in Δ f-15 kHz.

The reference signal is described in more detail.

The CRS is a reference signal for obtaining information on a channel state shared by all UEs within a cell and a measurement for handover, etc. The DM-RS is used to demodulate data only for a specific UE. Information for demodulation and channel measurement may be provided using such reference signals. That is, the DM-RS is used only for data demodulation, and the CRS is used for two purposes of channel information acquisition and data demodulation.

The receiver side (i.e., the terminal) measures a channel state from the CRS, and feeds back an indication related to channel quality, such as a Channel Quality Indication (CQI), a Precoding Matrix Index (PMI), and/or a Rank Indication (RI), to the transmission side (i.e., the eNB). CRS is also known as cell-specific RS. Conversely, a reference signal related to feedback of Channel State Information (CSI) may be defined as a CSI-RS.

The DM-RS may be transmitted via the resource element when data demodulation on the PDSCH is required. The terminal may receive whether DM-RS exists via an upper layer and is valid only when a corresponding PDSCH is mapped. The DM-RS may be referred to as UE-specific RS or demodulation RS (dmrs).

Referring to fig. 14, as a unit in which a reference signal is mapped, a downlink resource block pair may be represented by 12 subcarriers in one subframe x frequency domain in a time domain. That is, one resource block pair has a length of 14 OFDM symbols in the case of a normal Cyclic Prefix (CP) (fig. 14(a)), and has a length of 12 OFDM symbols in the case of an extended Cyclic Prefix (CP) (fig. 14 (b)). Resource Elements (REs) denoted by "0", "1", "2", and "3" in the resource block grid refer to positions of CRSs of antenna port indexes "0", "1", "2", and "3", respectively, and resource elements denoted by "D" refer to positions of DM-RSs.

Hereinafter, when the CRS is described in more detail, the CRS is used to estimate channels of physical antennas and is distributed in an entire frequency band as a reference signal that may be generally received by all terminals located in a cell. That is, the CRS is transmitted as a cell-specific signal over a wide band in each subframe. In addition, CRS may be used for channel quality information (CSI) and data demodulation.

CRS is defined in various formats according to an antenna array on the transmitter side (eNB). The RS is transmitted based on a maximum of 4 antenna ports according to the number of transmit antennas of the eNB in the 3GPP LTE system (e.g., release 8). The transmitter side has three types of antenna arrays of three single transmit antennas, two transmit antennas and four transmit antennas. For example, in case the number of transmit antennas of the eNB is 2, CRSs for the antenna #1 and the antenna #2 are transmitted. For another example, in case the number of transmit antennas of the eNB is 4, CRSs for the antennas #1 to #4 are transmitted.

When the eNB uses a single transmit antenna, reference signals for a single antenna port are arranged.

When the eNB uses two transmit antennas, reference signals for the two transmit antenna ports are arranged by using a Time Division Multiplexing (TDM) scheme and/or a Frequency Division Multiplexing (FDM) scheme. That is, different time resources and/or different frequency resources are allocated to reference signals for two antenna ports different from each other.

In addition, when the eNB uses four transmit antennas, reference signals for the four transmit antenna ports are arranged using a TDM and/or FDM scheme. The channel information measured by the downlink signal reception side (i.e., terminal) can be used to demodulate data transmitted by using a transmission scheme such as single transmit antenna transmission, transmit diversity, closed loop spatial multiplexing, open loop spatial multiplexing, or multi-user MIMO.

In the case of supporting MIMO antennas, when a reference signal is transmitted from a specific antenna port, the reference signal is transmitted to a location of a specific resource element in a pattern of the reference signal and is not transmitted to a location of a specific resource element for another antenna port. That is, the reference signals among different antennas are not duplicated to each other.

The rules for mapping CRS to resource blocks are defined as follows.

[ equation 12]

k＝6m+(v+v_shift)mod 6

In equation 12, k and l denote a subcarrier index and a symbol index, respectively, and p denotes an antenna port. N _ symb ^ DL denotes the number of OFDM symbols in one downlink slot, and N _ RB ^ DL denotes the number of radio resources allocated to the downlink. N _ s represents a slot index, and N _ ID ^ Cell represents a Cell ID. mod denotes a modulo operation. The position of the reference signal varies according to the v _ shift value in the frequency domain. Since v _ shift depends on a cell ID (i.e., a physical layer cell ID), the position of the reference signal has various frequency shift values according to the cell.

In more detail, the location of the CRS may be shifted in the frequency domain by cell in order to improve channel estimation performance via the CRS. For example, when the reference signals are arranged at intervals of three subcarriers, the reference signals are allocated to the 3 k-th subcarrier in one cell and the reference signals are allocated to the 3k + 1-th subcarrier in another cell. With respect to one antenna port, the reference signals are arranged at intervals of six resource elements in the frequency domain, and are separated from the reference signals allocated to another antenna port at intervals of three resource elements.

In the time domain, the reference signals are arranged at a constant interval from the symbol index 0 of each slot. The time interval is defined differently according to the cyclic shift length. In case of the normal cyclic shift, the reference signal is placed on

symbol indexes

0 and 4 of the slot, and in case of the extended CP, the reference signal is placed on

symbol indexes

0 and 3 of the slot. A reference signal for one antenna port having a maximum value between two antenna ports is defined in one OFDM symbol. Thus, in case of four transmit antenna transmission, reference signals for reference

signal antenna ports

0 and 1 are placed on symbol indexes 0 and 4 (

symbol indexes

0 and 3 in case of extended CP), and reference signals for

antenna ports

2 and 3 are placed on symbol index 1 of the slot. The positions of the reference signals for

antenna ports

2 and 3 in the frequency domain are interchanged in the second time slot.

Hereinafter, when describing the DM-RS in more detail, the DM-RS is used to demodulate data. When a terminal receives a reference signal, precoding weights for a specific terminal in MIMO antenna transmission are used without change in order to estimate a channel related to and corresponding to a transmission channel transmitted in each transmit antenna.

The 3GPP LTE system (e.g., release 8) supports a maximum of four transmit antennas, and DM-RS for rank 1 beamforming is defined. The DM-RS for rank 1 beamforming also refers to a reference signal for antenna port index 5.

A rule for mapping DM-RS to resource blocks is defined as follows. Equation 13 shows the case of the normal CP, and equation 14 shows the case of the extended CP.

[ equation 13]

[ equation 14]

In

equations

13 and 14, k and l indicate a subcarrier index and a symbol index, respectively, and p indicates an antenna port. N _ sc ^ RB is the size of the resource block in the frequency domain and can be expressed as the number of subcarriers. n _ PRB indicates the number of physical resource blocks. N _ RB ^ PDSCH indicates the frequency band of resource blocks used for PDSCH transmission. N _ s indicates a slot index, and N _ ID ^ cell indicates a cell ID. Mod indicates modulo operation. The position of the reference signal varies according to the v _ shift value in the frequency domain. Since v _ shift depends on a cell ID (i.e., a physical layer cell ID), the position of the reference signal has various frequency shift values according to the cell.

UE procedures for receiving PDSCH

When the UE detects the PDCCH of the serving cell, DCI formats 1, 1A, 1B, 1C, 1D, 2A, 2B or 2C intended for the UE are carried on the serving cell except for the subframe indicated by the higher layer parameter "mbsfn-subframe configlist", the UE decodes the corresponding PDSCH in the same subframe by means of the restriction of the number of transport blocks defined in the higher layer.

The UE decodes the PDSCH according to the detected PDCCH with CRC scrambled by the SI-RNTI or P-RNTI on which the DCI format 1A, 1C intended for the UE is carried, and assumes that the PRS does not exist in the Resource Blocks (RBs) on which the corresponding PDSCH is carried.

A UE in which a Carrier Indicator Field (CIF) for a serving cell is configured assumes that the CIF is not present in any PDCCH of the serving cell within the common search space.

Otherwise, when the PDCCH CRC is scrambled by the C-RNTI or the SPS C-RNTI, wherein the UE configuring the CIF assumes that the CIF for the serving cell exists in the PDCCH, the PDCCH is set within the UE-specific search space.

When the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the SI-RNTI, the UE decodes the PDCCH and the corresponding PDSCH in the combination defined in table 3 below. PDSCH corresponding to PDCCH is scrambled by SI-RNTI initialization.

Table 3 illustrates a PDCCH and a PDSCH configured by SI-RNTI.

[ Table 3]

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the P-RNTI, the UE decodes the PDCCH and the corresponding PDSCH in a combination defined in Table 4 below. PDSCH corresponding to PDCCH is initially scrambled by P-RNTI.

Table 4 illustrates a PDCCH and a PDSCH configured by a P-RNTI.

[ Table 4]

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the RA-RNTI, the UE decodes the PDCCH and the corresponding PDSCH in a combination defined in Table 5 below. PDSCH corresponding to PDCCH is initialized to be scrambled by RA-RNTI.

Table 5 illustrates a PDCCH and a PDSCH configured by RA-RNTI.

[ Table 5]

The UE may be semi-statically configured via higher layer signaling such that it receives PDSCH data transmissions signaled via the PDCCH in any of 9 transmission modes (including mode 1 through mode 9).

In the case of the frame structure type 1,

the UE does not receive PDSCH RBs transmitted in antenna port 5 even in any subframe where the number of OFDM symbols for PDCCH with common CP is 4.

-if any of the 2 Physical Resource Blocks (PRBs) to which a Virtual Resource Block (VRB) pair is mapped overlaps the PBCH or the frequency at which the primary or secondary synchronization signal is transmitted within the same subframe, the UE does not receive the PDSCH RBs transmitted in

antenna ports

5, 7, 8, 9, 10, 11, 12, 13 or 14 in the respective 2 PRBs.

The UE does not receive PDSCH RBs transmitted in the antenna port 7 to which the distributed VRB resource allocation has been allocated.

-if the UE does not receive all allocated PDSCH RBs, the UE may skip decoding of the transport blocks. If the UE skips this decoding, the physical layer indicates that the transport block was not successfully decoded for the higher layers.

In the case of the frame structure type 2,

-if any of the 2 PRBs to which the VRB is mapped overlaps the frequency at which the PBCH is transmitted within the same subframe, the UE does not receive the PDSCH RB transmitted in antenna port 5 in the corresponding 2 PRBs.

-if any of the 2 PRBs to which the VRB pair is mapped overlaps a frequency in which the primary or secondary synchronization signal is transmitted within the same subframe, the UE does not receive PDSCH RBs transmitted in

antenna port

7, 8, 9, 10, 11, 12, 13 or 14 in the corresponding 2 PRBs.

-if the common CP is configured, the UE does not receive PDSCH in the antenna port 5 where the distributed VRB resource allocation has been allocated within a special subframe of uplink-downlink configuration #1 or # 6.

The UE does not receive the PDSCH transmitted in the antenna port 7 to which the distributed VRB resource allocation has been allocated.

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the C-RNTI, the UE decodes the PDCCH and the corresponding PDSCH in each combination defined in Table 6 below. PDSCH corresponding to PDCCH is initialized to be scrambled by C-RNTI.

If the CIF for the serving cell is configured in the UE or the UE is configured by a higher layer such that it decodes the PDCCH having the CRC scrambled by the C-RNTI, the UE decodes the PDSCH of the serving cell indicated by the CIF value within the decoded PDCCH.

When a UE of

transmission mode

3, 4, 8 or 9 receives a DCI format 1A allocation, the UE assumes that PDSCH transmissions related to transport block 1 and transport block 2 are prohibited.

If the UE is set to transmission mode 7, a UE-specific reference signal corresponding to the PDCCH is initially scrambled by the C-RNTI.

If extended CP is used in downlink, the UE does not support transmission mode 8.

If the UE is set to transmission mode 9, when the UE detects a PDCCH having a CRC scrambled by a C-RNTI carrying a DCI format 1A or 2C intended for the UE thereon, the UE decodes the corresponding PDSCH in a subframe indicated by a higher layer parameter "mbsfn-subframe configlist". However, subframes configured by a higher layer to decode PMCH or subframes configured by a higher layer to be part of PRS instants are excluded, PRS instants are configured only within MBSFN subframes, and the length of CP used in subframe #0 is a common CP.

Table 6 illustrates a PDCCH and a PDSCH configured by C-RNTI.

[ Table 6]

If the UE is configured by the higher layer such that it decodes the PDCCH with the CRC scrambled by the SPS C-RNTI, the UE decodes the PDCCH of the primary cell and the corresponding PDSCH of the primary cell in each combination defined in Table 7 below. The same PDSCH related configuration is applied if the PDSCH can be transmitted without the corresponding PDCCH. PDSCH corresponding to PDCCH and PDSCH without PDCCH are initially scrambled by SPS C-RNTI.

If the UE is set to transmission mode 7, the PDCCH and the corresponding UE-specific reference signal are initially scrambled by the SPS C-RNTI.

If the UE is set to transmission mode 9, when the UE detects a PDCCH having a CRC scrambled by an SPS C-RNTI carrying thereon a DCI format 1A or 2C intended for the UE, or a PDSCH not requiring PDCCH configuration intended for the UE, the UE decodes the corresponding PDSCH in a subframe indicated by a higher layer parameter "subframeconfiglist". However, a subframe configured by a higher layer to decode PMCH or a subframe configured by a higher layer to be a part of PRS timing is excluded, PRS timing is configured only within an MBSFN subframe, and the length of CP used in subframe #0 is a general CP.

Table 7 illustrates a PDCCH and a PDSCH configured by SPS C-RNTI.

[ Table 7]

If the UE is configured by a higher layer such that it decodes the PDCCH having the CRC scrambled by the temporary C-RNTI and is configured not to decode the PDCCH having the CRC scrambled by the C-RNTI, the UE decodes the PDCCH and the corresponding PDSCH in combination as defined in Table 8. PDSCH corresponding to PDCCH is initially scrambled by a temporary C-RNTI.

Table 8 illustrates a PDCCH and a PDSCH configured by the temporary C-RNTI.

[ Table 8]

UE procedures for PUSCH transmission

The UE is semi-statically configured via higher layer signaling such that it performs PUSCH transmission signaled via PDCCH in accordance with either of two types of

uplink transmission modes

1 and 2 defined in table 9 below. If the UE is configured by a higher layer such that it decodes the PDCCH having the CRC scrambled by the C-RNTI, the UE decodes the PDCCH in the combination defined in Table 9 and transmits a corresponding PUSCH. PUSCH transmissions corresponding to PDCCH and PUSCH repeated transmissions for the same transport block are initially scrambled by C-RNTI. Transmission mode 1 is the default uplink transmission mode until the uplink transmission mode is allocated in the UE by higher layer signaling.

When the UE is configured to transmission mode 2 and receives the DCI format 0 uplink scheduling grant, the UE assumes that PUSCH transmission related to transport block 1 and transport block 2 is prohibited.

Table 9 illustrates PDCCH and PUSCH configured by C-RNTI.

[ Table 9]

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the C-RNTI and is also configured to receive a random access procedure initiated by a PDCCH order, the UE decodes the PDCCH in accordance with a combination defined in Table 10 below.

Table 10 illustrates a PDCCH set as a PDCCH order for starting a random access procedure.

[ Table 10]

DCI format	Search space
		DCI format 1A	Generic and C-RNTI UE-specific

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the SPS C-RNTI, the UE decodes the PDCCH in the combination defined in Table 11 below and transmits the corresponding PUSCH. PUSCH transmissions corresponding to PDCCH and PUSCH repeated transmissions for the same transport block are initially scrambled by SPS C-RNTI. The repeated transmission of PUSCH for the same transport block as the minimum transmission of PUSCH is initially scrambled by SPS C-RNTI without the corresponding PDCCH.

Table 11 illustrates PDCCH and PUSCH configured by SPS C-RNTI.

[ Table 11]

If the UE is configured by a higher layer such that the UE decodes the PDCCH in the combination defined in Table 12 regardless of whether the UE has been configured to decode the PDCCH having the CRC scrambled by the C-RNTI, which decodes the PDCCH scrambled by the temporary C-RNTI, and transmits the corresponding PDSCH. The PUSCH corresponding to the PDCCH is initially scrambled by the temporary C-RNTI.

The PUSCH transmission corresponding to the random access response grant and the PUSCH repeated transmission for the same transport block are scrambled by the temporary C-RNTI if the temporary C-RNTI is set by a higher layer. Otherwise, the PUSCH transmission corresponding to the random access response grant and the PUSCH repeated transmission for the same transport block are initially scrambled by the C-RNTI.

Table 12 illustrates a PDCCH configured by the temporary C-RNTI.

[ Table 12]

DCI format	Search space
		DCI format
0	General purpose

If the UE is configured by a higher layer such that it decodes the PDCCH having the CRC scrambled by the TPC-PUCCH-RNTI, the UE decodes the PDCCH in the combination defined in Table 13 below. In table 13, the indication "3/3 a" means that the UE receives DCI format 3 or DCI format according to the configuration.

Table 13 illustrates a PDCCH configured by TPC-PUCCH-RNTI.

[ Table 13]

DCI format	Search space
		DCI format
3/3A	General purpose

If the UE is configured by a higher layer such that it decodes the PDCCH with the CRC scrambled by the TPC-PUSCH-RNTI, the UE decodes the PDCCH in the combination defined in Table 14 below. In table 14, an indication "3/3 a" includes that the UE receives DCI format 3 or DCI format according to the configuration.

Table 14 illustrates a PDCCH configured by TPC-PUSCH-RNTI.

[ Table 14]

DCI format	Search space
		DCI format
3/3A	General purpose

Cross-carrier scheduling and E-PDCCH scheduling

In the 3GPP LTE Rel-10 system, in a case where a plurality of Component Carriers (CCs) ═ serving cells have been aggregated, a cross-CC scheduling operation is defined as follows. One CC (i.e., a scheduled CC) may be previously configured such that DL/UL scheduling is performed only by a specific one CC (i.e., a scheduled CC) (i.e., such that a DL/UL grant PDCCH for the corresponding scheduled CC is received). Also, the corresponding scheduling CC may basically perform DL/UL scheduling. In other words, a Search Space (SS) for scheduling a PDCCH of a scheduled/scheduled CC within a cross-CC scheduling correlation may exist entirely within a control channel region of the scheduling CC.

In the LTE system, as described above, the FDD DL carrier or TDD DL subframe transmits PDCCH, PHICH and PCFICH using the first n OFDM symbols of the subframe, i.e., it is a physical channel for transmitting various types of control information, and uses the remaining OFDM symbols for PDSCH transmission. In this case, the number of symbols used for control channel transmission in each subframe is transmitted to the UE in a semi-static manner via a physical channel, such as PCFICH, dynamically or via RRC signaling. In this case, the value of "n" may be set to 1 symbol to at most 4 symbols, characteristically, according to subframe characteristics and system characteristics (e.g., FDD/TDD or system bandwidth).

In the existing LTE system, the PDCCH is a physical channel for DL/UL scheduling and various types of control information transmission, which has limitations because it is transmitted via limited OFDM symbols.

Thus, an enhanced PDCCH (i.e., E-PDCCH) may be introduced (which is more freely multiplexed to the PDSCH using the FDM/TDM method) rather than a control channel transmitted via an OFDM symbol separate from the PDSCH like the PDCCH.

Referring to fig. 15, a legacy PDCCH (i.e., L-PDCCH) is transmitted in the first n OFDM symbols of a subframe, and an E-PDCCH is multiplexed to a PDSCH using an FDM/TDM method and transmitted.

Quasi co-location (QCL) between antenna ports

Quasi co-location and quasi co-location (QC/QCL) can be defined as follows.

If two antenna ports have (or experience) a QC/QCL relationship, the UE may assume that the large scale characteristics of the signal transmitted via one antenna port may be inferred from the signal transmitted via the other antenna port. In this case, the large-scale characteristics include one or more of delay spread, doppler shift, average received power, and reception timing.

In addition, the following may be defined. Assuming that the two antenna ports have (or experience) a QC/QCL relationship, the UE may assume that large-scale properties of the channel of one symbol transmitted via one antenna port may be inferred from the wireless channel of one symbol transmitted via the other antenna port. In this case, the large-scale attributes include one or more of delay spread, doppler shift, average gain, and average delay.

That is, if two antenna ports have a QC/QCL relationship (or experience QC/QCL), this means that the large scale characteristics of the wireless channel from one antenna port are the same as the large scale characteristics of the wireless channel from the other antenna port. Assuming that a plurality of antenna ports in which RSs are transmitted are considered, if the antenna ports on which two types of different RSs are transmitted have QCL relationships, the large-scale characteristics of the wireless channel from one antenna port may be replaced with the large-scale characteristics of the wireless channel from another antenna port.

In this specification, QC/QCL related definitions are not distinguished. That is, the QC/QCL concept may follow one of the definitions. In a similar fashion, the QC/QCL concept definition may change in the form of an antenna port with established QC/QCL assumptions may be assumed to be transmitted at the same location (i.e., co-located) (e.g., a UE may assume that the antenna port is an antenna port transmitting on the same transmission point). The spirit of the present invention includes such similar modifications. In the embodiments of the present invention, for convenience of description, the QC/QCL-related definitions may be used interchangeably.

In terms of the concept of QC/QCL, a UE may not necessarily assume the same large scale characteristics between wireless channels from respective antenna ports relative to non-QC/QCL antenna ports. That is, in this case, the UE may perform independent processing for timing acquisition and tracking, frequency offset estimation and compensation, delay estimation, and doppler estimation for each configured non-QC/QCL antenna port.

There is an advantage in that the UE can perform the following operations between antenna ports that can assume QC/QCL:

the UE may equally apply the power delay profile, delay spread and doppler spectrum with respect to delay spread and doppler spread, and the result of doppler spread estimation for the wireless channel from any one antenna port to a Wiener (Wiener) filter, which is used for channel estimation of the wireless channel from other antenna ports.

With respect to frequency shift and reception timing, the UE may perform time and frequency synchronization on any one antenna port and then apply the same synchronization to the demodulation of the other antenna ports.

-the UE may average Reference Signal Received Power (RSRP) measurements for two or more antenna ports with respect to the average received power.

For example, if DMRS antenna ports used for downlink data channel demodulation have undergone QC/QCL with CRS antenna ports of a serving cell, the UE may apply large-scale characteristics of a wireless channel estimated from its own CRS antenna port to channel estimation via the corresponding DMRS antenna ports in the same manner, thereby improving reception performance of the DMRS-based downlink data channel.

The reason for the above operation is that estimates on large-scale characteristics can be obtained more stably from CRS, since CRS is a reference signal that is broadcast at a relatively high density per subframe and in full bandwidth. In contrast, DMRS is transmitted in a UE-specific manner for a specific scheduled RB, and a precoding matrix used by the eNB for a Precoding Resource Group (PRG) element for transmission may be changed. Accordingly, the effective channel received by the UE may change in units of PRGs. Accordingly, although a plurality of PRGs have been scheduled in the UE, performance degradation may occur when DMRS is used to estimate large-scale characteristics of a wireless channel over a wide frequency band. In addition, the CSI-RS may also have a transmission period of several to several tens of ms, and each resource block also has a low density of 1 resource element, which is used for each antenna port on average. Therefore, the CSI-RS may experience performance degradation if it is used to estimate the large scale characteristics of the wireless channel.

That is, the UE may perform detection/reception, channel estimation, and channel state reporting of downlink reference signals via QC/QCL hypotheses between antenna ports.

Method for transmitting and receiving data in unauthorized band

One embodiment of the present invention proposes a technique regarding a method of enabling a UE to directly determine a transmission opportunity (TXOP) period, or a Reserved Resource Period (RRP), by detecting a specific signal (e.g., preamble, synchronization signal, CRS, CSI-RS, etc.) through a process such as blind detection in the case where signals are transmitted and received via carriers of an unlicensed band.

Hereinafter, in this specification, the time period in which the eNB and the UE have occupied/guaranteed respective carrier resources so as to transmit signals via a carrier of an unlicensed band/spectrum is collectively referred to as RRP.

In this case, the RRP may be defined to be substantially limited to a single continuous period of time, or may be defined in the form of a group of a plurality of continuous periods of time. For example, the RRP may include units of symbols, slots, subframes, radio frames, and so on.

The name of the base station described in this specification is used as a comprehensive term including a Radio Remote Head (RRH), an eNB, a Transmission Point (TP), a Reception Point (RP), and a relay station.

Hereinafter, for convenience of description, a proposed method based on the 3GPP LTE/LTE-a system is described below. However, the scope of the system to which the proposed method is applicable may be extended to other systems (e.g., UTRA) than the 3GPP LTE/LTE-a system.

In 3GPP, as mobile communication data traffic has been explosively increased, a service of an unlicensed band/spectrum (that is, Licensed Assisted Access (LAA)) has been proposed as one of schemes for satisfying the rapid increase of mobile communication data traffic. LAA refers to a technique of aggregating an LTE licensed band and an unlicensed band/spectrum into one band using Carrier Aggregation (CA). The LAA is described below with reference to fig. 16.

In the case where Component Carriers (CCs) (or cells) of the licensed band and CCs (or cells) of the unlicensed band have undergone carrier aggregation as in fig. 16, the eNB may transmit a signal to the UE, or the UE may transmit a signal to the eNB.

Hereinafter, for convenience of description, the licensed band is referred to as an "LTE-a band", and the unlicensed band/spectrum is referred to as an "LTE-U band" as compared to the LTA-a band.

Hereinafter, in the description of the embodiments of the present invention, for convenience of describing the method proposed in the embodiments of the present invention, a case where a UE has been configured to perform wireless communication via two CCs in a licensed band and an unlicensed band/spectrum is assumed. In this case, for example, the carrier of the licensed band may be considered as a primary component carrier (PCC or PCell), and the carrier of the unlicensed band/spectrum may be considered as a secondary component carrier (SCC or SCell).

However, the method proposed in the embodiment of the present invention can be extended and applied to a case where a plurality of licensed bands and a plurality of unlicensed bands are used as a carrier aggregation scheme. Furthermore, the method may also be extended and applied to a case where only the unlicensed band/spectrum undergoes carrier aggregation, or only the licensed band undergoes carrier aggregation, and transmission and reception of signals are performed between the eNB and the UE. Furthermore, the method proposed in the embodiments of the present invention may also be extended and applied to systems having other features than the 3GPP LTE system.

The LTE-U band refers to a dedicated band that does not guarantee a specific system. Therefore, in order for the eNB and the UE to perform communication in the LTE-U band, the respective bands need to be occupied/guaranteed during a specific time period (i.e., RRP) via contention with other communication systems not related to LTE, such as Wi-Fi (i.e., 802.11 systems), because the respective bands are unlicensed spectrum.

To occupy such an RRP, several methods are possible. As a representative method, there may be a method in which an eNB and/or a UE transmits a specific reservation signal or continues to transmit an RS and a data signal such that a signal of a specific power level or more signals continue to be transmitted during an RRP in order for other communication systems, such as a Wi-Fi system, to recognize that a corresponding radio channel is busy.

In this case, the eNB may perform Clear Channel Assessment (CCA) alone in the LTE-U band and inform the RRP occupied by the UE. For example, if operation of an uplink/downlink band for an FDD system is supported in the LTE-U band, only the eNB may perform CCA in the LTE-U band and occupy RRP.

In contrast, the UE and the eNB may autonomously occupy resources of the LTE-U band by performing CCA. For example, if TDD operation is supported in the LTE-U band or operation of an uplink band for an FDD system is supported in the LTE-U band, the UE and the eNB may occupy RRPs in the LTE-U band by performing CCA.

If the eNB has previously determined the RRP period to be occupied in the LTE-U band, it may previously inform the UE of the RRP period so that the UE may maintain the communication transmission/reception link during the corresponding indicated RRP.

The method for informing the UE of the corresponding RRP period information by the eNB may include a method for explicitly transmitting the corresponding RRP period information via another CC (e.g., LTE-a band) connected in the carrier aggregation scheme.

For example, the eNB may transmit information about a time point at which the RRP is initiated and a time point (e.g., a slot number or a subframe index) at which the RRP is ended to the UE, and may transmit information about a time point (e.g., a slot number or a subframe index) at which the RRP is initiated and a length (e.g., a slot or a subframe number) of the RRP to the UE.

However, as described above, the method for transmitting RRP information in the explicit indication scheme has a limitation in which a predictable data traffic amount must be calculated in advance, and the state of a wireless communication channel link in the LTE-U band can be expected to some extent. That is, if the interference environment is seriously changed during the RRP, and in case of an environment where the serious change of the interference environment is not easily expected, there is a problem that additional signaling may continue to be generated, such as the RRP must be further extended beyond its initial expectation, and when an error is generated in signaling exchange, a normal communication link cannot be guaranteed.

Accordingly, embodiments of the present invention propose a method for enabling a UE to detect a reference signal of a corresponding unlicensed band/spectrum, and attempt detection in a blind detection scheme, in addition to such an explicit RRP indication method, and to identify a detected period as a RRP.

Fig. 17 is a diagram illustrating a method of transmitting and receiving data in an unlicensed band/spectrum according to an embodiment of the present invention.

Referring to fig. 17, an eNB (and/or a UE) performs CCA in an unlicensed band/spectrum (i.e., LTE-U band) at step S1701.

For example, prior to the start of a transmission, the eNB (and/or UE) may perform a CCA for sensing the medium of a wireless channel or LTE-U band during a certain time period (e.g., a DCF interframe space (DIFS) period in accordance with IEEE 802.11).

The eNB (and/or UE) transmits (or broadcasts) a reference signal and/or a preamble (or midamble) during its busy period (i.e., RRP) at step S1702.

That is, if the eNB (and/or UE) performs CCA and determines that the medium is not occupied in the LTE-U band, the eNB (and/or UE) transmits an RS (e.g., CRS, CSI-RS, DM-RS, SRS, etc.) and/or a preamble/midamble during RRP.

In other words, in order to transmit downlink data (i.e., downlink band in case of FDD, and downlink subframe in case of TDD), or receive uplink data (i.e., uplink band in case of FDD, and uplink subframe in case of TDD), the eNB continues to transmit the RS and/or preamble/midamble when the eNB needs to occupy the medium. Likewise, when the UE needs to occupy the medium, the UE continues to transmit the RS and/or the preamble/midamble in order to transmit the uplink (i.e., uplink band in case of FDD and uplink subframe in case of TDD).

In this case, the RRP may be determined to be a variable length according to the amount of data to be transmitted or received, but may be set to a fixed length in advance.

The RRP may be independently determined for each CC (or cell) if multiple CCs (or cells) have been configured in the UE in an unlicensed band/spectrum. Accordingly, the eNB (and/or UE) may independently determine the RRP for each CC (or cell) by performing CCA, and may transmit the RS and/or the preamble/midamble for each CC (or cell).

If the reference signal and/or the preamble/midamble are transmitted during the RRP as described above, devices of other wireless communication systems other than the eNB and/or the UE may also determine that the medium has been occupied by the eNB and/or the UE during the RRP.

If it is detected at step S1701 that the medium is in an occupied state in the LTE-U band, the eNB (and/or UE) does not start its own transmission. In this case, the eNB (and/or UE) may wait for a delay time (e.g., a random backoff period) for medium access and then attempt to transmit a signal again (i.e., perform CCA).

Fig. 18 is a diagram illustrating a method of transmitting and receiving data in an unlicensed band/spectrum according to an embodiment of the present invention.

Fig. 18 illustrates operation of a corresponding device for detecting a reference signal and/or a preamble/midamble within a RRP, which is transmitted by an apparatus performing CCA as in fig. 17.

Referring to fig. 18, the UE (and/or eNB) performs blind detection in order to detect a predetermined specific signal at step S1801.

In this case, the predetermined specific signal may be, for example, an RS and/or a preamble (or a midamble).

For example, the UE may continue to perform blind detection on the reference signal and/or the preamble/midamble in order to determine the RRP from a point in time at which carrier aggregation is configured with respect to CCs belonging to the LTE-U band via an RRC connection reconfiguration message from the eNB or the like.

The UE (and/or eNB) determines a period of detecting a predetermined specific signal via blind detection as an RRP at step S1802.

In this case, the UE (and/or eNB) may detect the RS and/or the preamble (midamble) via blind detection, may determine a starting point of the RRP, and may not perform the blind detection during a specific time.

As described above, in order for a UE to autonomously determine an RRP in an LTE-U band, there is a need for blind detection information (hereinafter, "RRP configuration information") for Reference Signals (RSs) and/or preamble/midamble and RRP determination.

Fig. 19 is a diagram illustrating a method of transmitting and receiving data in an unlicensed band/spectrum according to an embodiment of the present invention.

Referring to fig. 19, in order for the UE to autonomously determine the RRP in the LTE-U band, the eNB may previously transmit various parameters (i.e., RRP configuration information) necessary for blind detection of a Reference Signal (RS) and/or a preamble/midamble and RRP determination to the UE at step S1901.

In this case, the eNB may transmit the RRP configuration information to the UE via higher layer signaling (e.g., RRC signaling or MAC control element).

Further, such RRP configuration information may be transmitted to the UE via a serving cell (e.g., PCell or SCell) of the LTE-a band.

To determine the RRP, the UE may use an RS (e.g., CRS, CSI-RS, etc.) and/or a preamble/midamble.

If the RRP can be determined using only the RS, only the RS-related information may be defined as RRP configuration information and may be provided to the UE.

In contrast, if the RRP can be determined based on only the preamble/midamble, only the preamble/midamble-related information may be defined as RRP configuration information and provided to the UE. Also, in this case, the RRP is determined via the preamble/midamble, but RS-related information is also included in the RRP configuration information for blind detection of the RS by the UE in the subsequent subframe, and may be provided to the UE.

Alternatively, if the RRP can be determined using two signals of the RS and the preamble/midamble, both the RS-related information and the preamble/midamble-related information may be defined as RRP configuration information and provided to the UE.

Further, the RRP configuration information may be fixed and known in advance to both the UE and the eNB. In this case, the eNB may not provide the RRP configuration information to the UE. That is, step S1901 may not be performed.

Hereinafter, the RRP configuration information will be described in more detail below.

The eNB may provide at least one of the following parameters as RRP configuration information.

RS-related information is to undergo blind detection in LTE-U band

For purposes such as CoMP, the following information elements may be configured as one set, and RS-related information may be provided as two or more sets.

Hereinafter, for convenience of description, an example in which an RS is a CRS for the purpose of specifying a "cell" is mainly described. In this case, the present invention is not limited to this example, and another RS, such as a CSI-RS, may be used to determine the RRP so as to designate "TP". In this case, some similar information may be provided as information on another RS, such as a CSI-RS, according to the corresponding RS.

1) RS sequence scrambling initialization parameter (or CRS sequence scrambling initialization parameter)

For example, if CRS is used for RRP determination, physical cell IDs (e.g., 0 to 503) may correspond to such use.

Alternatively, if CSI-RS is used for RRP determination, the TP-specific scrambling ID may correspond to such use.

2) Number of RS ports/number of RS ports

For example, if CRS is used for RRP determination, the CRS antenna port number may be directly indicated (e.g., antenna ports 0, 1), or the CRS antenna port number may be indirectly indicated as information on the CRS antenna port number (e.g., the number of antenna ports 2 indicates antenna ports 0, 1).

Alternatively, if CRS-RS is used for RRP determination, the CRS-RS antenna port number may be directly indicated (e.g., antenna ports 15, 16), or the CRS antenna port number may be indirectly indicated as information on the CRS antenna port number (e.g., the number of antenna ports 2 indicates antenna ports 15, 16).

3) Information for identifying radio frame boundaries

For example, a slot number offset or a subframe offset value compared to the reference cell timing may be provided.

In this case, the reference cell may be previously fixed to a specific cell or may be designated by the eNB.

For example, the reference cell may be defined as a serving cell corresponding to a CC on which higher layer signaling including such RRP configuration information is carried. Also, the reference cell may be defined as a serving cell of a PCell corresponding to the corresponding UE. Further, an explicit indication (e.g., cell ID or index ("ServCellIndex")) may be provided indicating that the serving cell corresponding to the particular CC is designated as the reference cell.

In this case, if a floating radio frame boundary described later is applied, the boundary of the radio frame is started from a time point (i.e., a subframe index and a slot number are increased from #0) at which the CRC is detected, or after a certain offset from the time point at which the CRC is detected. Therefore, the information providing the radio frame boundary notification can be omitted.

Further, if the boundaries of the reference cell and the radio frame have been aligned, the information providing notification of the boundaries of the radio frame may be omitted.

4) MBSFN subframe configuration

In MBSFN subframes, CRS is transmitted only within non-MBSFN areas of the MBSFN subframe. The MBSFN subframe is divided into a non-MBSFN area and an MBSFN area. A non-MBSFN area is defined as the first n (e.g., 1 or 2) OFDM symbols of an MBSFN subframe. MBSFN areas within an MBSFN subframe are defined as OFDM symbols except for non-MBSFN areas.

The MBSFN subframe configuration information is formed in a bitmap form, for example, and a subframe may be indicated in each bit of the bitmap. For example, "1" may indicate an MBSFN subframe, and "0" may indicate a non-MBSFN subframe, and vice versa.

Thus, if MBSFN subframe configuration information is provided, CRS transmission symbols are restricted to the PDCCH region only (e.g., the first 1 or 2 OFDMA symbols within the subframe) in the indicated corresponding indicated MBSFN subframe.

5) Information on transmission bandwidth of RS

The information on the transmission bandwidth of the RS may be indicated by the number of RBs.

In this case, it can be assumed that the transmission band of the RS is the same as the system bandwidth. In this case, information on the transmission bandwidth of the RS may not be included in the RRP configuration information.

6) Information on power level thresholds for RRP determination

This information may refer to information about a specific power level threshold at which a corresponding subframe should be determined to belong to the RRP for each subframe.

For example, if the power level threshold is set in units of subframes, the UE may determine that a subframe belongs to the RRP when an average reception power value of the RS REs is greater than or equal to the corresponding threshold in the corresponding subframe.

a) Such a power level threshold may be defined as a value for a subframe unit and/or an OFDM symbol unit (or another specific time unit), or may be set by the eNB.

In this case, the RRP may be subdivided and defined in units of OFDM symbols (or another specific time unit).

For example, if CRS is used for RRP determination, the UE determines whether an average reception power value of CRS REs for a corresponding OFDM symbol is greater than or equal to a threshold value based on the threshold value of each OFDM symbol. Further, the UE may determine that the OFDM symbol is an RRP from the OFDM symbol having the average reception power value greater than or equal to the threshold to the last OFDM symbol having the average reception power value greater than or equal to the threshold. Further, the UE may determine that the OFDM symbol is an RRP from an OFDM symbol whose average reception power value is greater than or equal to a threshold to an OFDM symbol whose average reception power value is less than the threshold.

Alternatively, the UE determines whether the average received power value is greater than or equal to a threshold value for each OFDM symbol (or in another specific time unit), but may determine the RRP for each subframe.

These are described in more detail. The UE may determine whether the average reception power value of the RS REs for the corresponding OFDM symbol is greater than or equal to a threshold value based on the threshold value of each OFDM symbol unit (or another specific time unit). If it is determined that all OFDM symbols (e.g., OFDM symbols in which RSs are transmitted) belonging to the corresponding subframe are successfully detected, the corresponding subframe may be defined or configured such that it is included in the RRP.

For example, if the CRS for antenna port 0 is used for RRP determination (in case of a general CP), the UE determines whether an average reception power value of 2 REs in the first OFDM symbol (l-0) of the first slot is greater than or equal to a threshold value, and if the average reception power value is greater than or equal to the threshold value, determines that the detection of the CRS is successful. In addition, the UE determines whether an average reception power value of 2 CRS REs in a fifth OFDM symbol (l ═ 4) of the first slot is greater than or equal to the threshold value, and determines that the detection of the CRS is successful if the average reception power value is greater than or equal to the threshold value. Likewise, the UE determines whether the detection of the CRS is successful with respect to the second slot in the same manner. As described above, the UE determines whether detection of the CRS is successful in each OFDM symbol in which the CRS is transmitted, and includes a corresponding subframe in the RRP if the CRS is successfully detected in all OFDM symbols of one subframe in which the CRS is transmitted.

Alternatively, the UE may determine whether the average reception power value of the RS REs for the corresponding OFDM symbol is greater than or equal to a threshold value based on the threshold value of each OFDM symbol (or another specific time unit). A respective subframe may be defined or configured to be included in the RRP if detection of the CRS is successful in determining at least L symbols of all OFDM symbols belonging to the respective subframe. For example, L may be a specific value of 1 or 2 or more.

For example, if the CRS for antenna port 0 is used for RRP determination (in case of a general CP), the UE determines whether an average reception power value of 2 REs in the first OFDM symbol (l-0) of the first slot is greater than or equal to a threshold value, and if the average reception power value is greater than or equal to the threshold value, determines that the detection of the CRS is successful. In addition, the UE determines whether an average reception power value of 2 CRS REs in a fifth OFDM symbol (l ═ 4) of the first slot is greater than or equal to the threshold value, and determines that the detection of the CRS is successful if the average reception power value is greater than or equal to the threshold value. Likewise, the UE determines whether the detection of the CRS is successful with respect to the second slot in the same manner. As described above, the UE determines whether detection of the CRS is successful in each OFDM symbol in which the CRS is transmitted, and includes a corresponding subframe in the RRP if the CRS is successfully detected in at least L OFDM symbols of one subframe in which the CRS is transmitted.

Accordingly, if the power level threshold is set for each OFDM symbol, a subframe including a specific number and above (or all the number of symbols) of OFDM symbols (whose average reception power value for CRS REs is greater than or equal to the power level threshold) may be determined to belong to an RRP.

7) Another RS information capable of QCL hypothesis and large-scale characteristics of wireless channel capable of QCL hypothesis at the time

This information is used with a stable reference to perform detection and demodulation of the corresponding RS.

For example, the large-scale characteristics may include one or more of delay spread, doppler shift, average gain, and average delay.

In this case, the QCL-capable RS may be an RS transmitted in the same CC (or cell) as that of the LTE-U band in which the CRS is transmitted, or may be an RS transmitted in another CC (or cell), for example, a serving cell of the LTE-a band.

a) RS information transmitted in the same CC and large-scale characteristics of QCL-capable assumed wireless channel

In this case, the RS transmitted in the same CC may be an RS corresponding to a specific preamble/midamble (scrambled by the initialization parameter N _ pre _ ID).

For example, if the CRS is used for RRP determination, the QCL hypothesis may be defined or configured between an antenna port related to the corresponding CRS and an antenna port related to another RS transmitted in the same CC as the CC in which the CRS is transmitted.

For example, in this case, the large scale characteristic that can be QCL assumed may be { doppler spread, doppler shift }.

Also, in this case, the RS corresponding to the preamble/midamble may have the same form as the sequence of the existing PSS/SSS. In this case, the conventional PSS/SSS and CRS for a particular cell can make QCL assumptions with respect to all large scale characteristics. In contrast, in this case, transmission of preambles in multiple cells, i.e., transmission in the form of a Single Frequency Network (SFN), may be considered. Thus, conventional operations may be modified and applied such that QCL assumptions apply only to the { doppler spread, doppler shift } characteristics.

b) RS information transmitted in another CC and large-scale characteristics of wireless channel that can QCL assume at the time

That is, the QCL hypothesis may be defined or configured between an antenna port related to the CRS and an antenna port related to another RS transmitted in a CC different from the CC in which the CRS is transmitted.

For example, in case of a specific RS of a different CC, a QCL having a CRS corresponding to a serving cell of the CC on which higher layer signaling including such RRP configuration information is transmitted, a QCL having a CRS corresponding to a serving cell of a PCell of a corresponding UE, and a QCL having a CRS corresponding to a serving cell of the specific CC (indicated by the eNB) may be indicated as being applied.

Characteristically, when the QCL assumes applicability between RSs of different CCs (i.e., between antenna ports) as described above (e.g., environments where two respective different CCs are transmitted at the same location (co-located) (e.g., transmission in the same eNB/TP)), the QCL assumption may be defined or configured such that it only applies to the characteristics of { doppler shift } or { doppler spread, doppler shift }.

For example, the UE may be based on the center frequency f at the PCell via such information_PcellAnd center frequency f of corresponding LTE-U band (SCell)_ScellBy correcting the Doppler shift estimate estimated from the CRS of the PCellDeriving Doppler shift values for corresponding SCells

Thus, detection performance for the corresponding SCell CRS may be performedAnd (5) lifting. This can be expressed in equation 15 below.

[ equation 15 ]

In equation 15, the function g includes a corresponding factor, and means that it may include other additional correction terms or coefficients.

In the case of doppler spread, if QCL assumptions are indicated as applicable, the detection performance of the corresponding RS can be improved in a similar manner using such information.

Also in this case, in addition, in an environment where the difference between (center) frequencies of different CCs is not more than a certain level, the characteristics of at least one of { delay spread, average delay } may be additionally defined or configured so that the QCL assumption is allowable. That is, if the difference between (center) frequencies of different CCs is not greater than a certain level, the characteristics of at least one of { delay spread, average delay } may be subject to QCL assumption in addition to the characteristics of { doppler shift } or { doppler spread, doppler shift }.

-information related to preamble/midamble undergoes blind detection in (optionally) LTE-U band

The following information units may be configured as one set for the purpose of detection such as multiple cell clusters, and preamble-related information may be provided using two or more sets.

1) Preamble sequence scrambling initialization parameter

For example, N _ pre _ ID (0 to X). In this case, X may be fixed to 503, or may be a value designated separately.

2) Information for identifying radio frame boundaries

For example, the reference cell may be defined as a serving cell of a CC on which higher layer signaling including such RRP configuration information is transmitted. Also, the reference cell may be defined as a serving cell of a PCell corresponding to the corresponding UE. Further, an explicit indication (e.g., cell ID or index ("ServCellIndex")) may be provided indicating that the serving cell of a particular CC is designated as a reference cell.

In this case, if the described floating radio frame boundary is applied, information providing notification of the radio frame boundary may be omitted because the boundary of the radio frame starts (i.e., the subframe index and slot number increase from #0), which increases from the time point at which the CRC is detected, and increases after a certain offset from the time point at which the CRC is detected.

Further, if the boundaries of the reference cell and the radio frame have been aligned, the information providing notification of the radio frame boundary may be omitted.

3) Information on transmission bandwidth of preamble

The information on the transmission bandwidth of the preamble may be represented by the number of RBs.

Further, the transmission bandwidth of the preamble may be fixed to Y RBs, for example. For example, the transmission bandwidth of the preamble may be Y-6, which is the same as a conventional synchronization signal.

4) Power level threshold information for RRP determination

When the average reception power value of the REs of the preamble is greater than or equal to a certain threshold, this information refers to the corresponding power level threshold information through which the corresponding preamble is determined to have been detected.

Blind detection of another cell/TP-specific RS, such as a CRS or CSI-RS, may be performed on subsequent consecutive subframes if the corresponding preamble is determined to have been detected by the detection condition.

In addition to the LTE-U band, the aforementioned RS QCL assumption may be equally applied between two or more (grant band) bands (or component carriers) in common between different CCs.

That is, in order to perform detection (and demodulation) of a specific RS in CC1 with a stable reference, a QCL hypothesis with a specific RS in CC2 may be defined or configured to be allowable. In other words, the QCL assumption may be set to be allowable between an antenna port related to a specific RS in the CC1 and an antenna port related to a specific RS in the CC 2.

In this case, the RS may correspond to a synchronization signal, a CRS, a CSI-RS, a DM-RS, an MBSFN RS, a PRS, or the like.

As described above, the large-scale characteristics of the wireless channel to which the QCL assumption between RSs of different CCs can be applicable can be defined or configured such that it only applies to the characteristics of { doppler shift } or { doppler spread, doppler shift } (e.g., environments in which two respective different CCs are in the same location (co-located) (e.g., transmission in the same eNB/TP)).

In this case, in addition, in an environment where the difference between (center) frequencies of different CCs is not more than a certain level, the characteristics of at least one of { delay spread, average delay } may be additionally defined or configured to be QCL-capable. That is, if the difference between (center) frequencies of different CCs is not greater than a certain level, the characteristics of at least one of { delay spread, average delay } may be subject to QCL assumption in addition to the characteristics of { doppler shift } or { doppler spread, doppler shift }.

In the proposed embodiment of the present invention, if a subframe in which the UE has succeeded in blind detection in the LTE-U band includes a specific preamble/midamble and/or RS, an operation for allowing the corresponding subframe to be identified as a starting subframe (i.e., subframe index #0) of a radio frame may be defined or configured.

Further, if the preamble/midamble and/or RS is detected at a predetermined specific location, such as the preamble/midamble and/or RS is detected right before the corresponding subframe, an operation for allowing the corresponding subframe to be identified as a starting subframe (i.e., subframe index #0) of the radio frame may be defined or configured. For example, due to a point of time at which the preamble is detected, a subframe after a predetermined specific time (e.g., after x OFDM symbols) may be identified as a starting subframe of the radio frame.

For example, the corresponding preamble/midamble may exist at a predetermined time period location and/or a predetermined frequency band, such as a particular fixed OFDM symbol index. For example, a conventional PSS/SSS sequence, which varies in the same form or in some modified form, may be applied as the corresponding preamble/midamble. Accordingly, the boundary of the radio frame (i.e., the boundary of the starting subframe of the radio frame) may be determined from a time point at which the preamble/midamble is transmitted (or detected), or after a certain time from the time point at which the preamble/midamble is transmitted (or detected).

Alternatively, without depending on the preamble/midamble, the UE may perform the operation for determining the starting point of the RRP by directly performing blind detection on the CRS of the subframe #0 without the preamble/midamble. For example, if the boundary of a subframe or symbol is already aligned with another CC (e.g., PCell), the UE may determine the starting point of the RRP only through the CRS without the preamble/midamble.

In this case, to reduce the complexity of blind detection, the range of time and/or frequency errors (e.g., 0.5ms) may be predetermined.

Such ranges of time and/or frequency errors may be communicated to the UE via network signaling, or may be predefined or set based on UE assumptions.

In this case, if the UE performs blind detection based on CRS (or CSI-RS) only, the UE must be allowed to obtain coarse timing because a synchronization signal, such as PSS, performing timing acquisition on the first stage does not exist.

Thus, information related to the time and/or frequency error range may be defined or set as such information, thereby being able to facilitate blind detection of the UE.

In this case, from a time point of view, if a Clear Channel Assessment (CCA) is determined at a point of time that deviates from the error range, the eNB may give up (or drop) the transmission of the signal.

Via such operation, in the LTE-U band, the boundary of the radio frame is not fixed, and the eNB may determine that the radio channel of the LTE-U band is idle. Accordingly, a floating radio frame boundary in the form of a radio frame start (e.g., transmission from subframe index #0) may be applied from a point in time at which transmission of a downlink frame starts. These will be described in more detail with reference to fig. 20.

Fig. 20 is a diagram illustrating a floating radio frame boundary according to an embodiment of the present invention.

In fig. 20, a first cell represents a reference cell (e.g., a PCell or a specific serving cell in a licensed band), and a second cell represents a cell in which an RRP is set in an unlicensed band/spectrum.

As described above, the RRP may start from a subframe in which a preamble/midamble and/or RS (e.g., CRS or CSI-RS) is transmitted, or the RRP may start after a predetermined specific time interval from a time point on which the preamble/midamble and/or RS is transmitted.

Further, as shown in fig. 20, a radio frame may start from a time point at which an RRP starts.

Therefore, among all subframe indexes and slot numbers defined within one radio frame, a subframe index has been configured or defined to grow from #0 and a slot number has also been configured or defined to grow from #0 based on a start point of a corresponding radio frame. Accordingly, RSs, such as CRS, CSI-RS, DMRS, SRS, and the like, undergo sequence generation based on parameters, such as slot number "n _ s" determined based on the boundary of the radio frame variably determined as described above. Accordingly, the UE can detect the corresponding RS.

For example, assume that the CSI-RS has a 5ms periodicity and has been configured to transmit in subframe #1 and subframe # 6.

In this case, if the subframe index of the reference cell is equally applicable in the RRP of the cell in the unlicensed band/spectrum, the position of the subframe in which the CSI-RS is transmitted is irregularly determined in the RRP based on the index of the subframe in which the RRP starts. For example, if the RRP starts from subframe #0, the CSI-RS is immediately transmitted in the next subframe (i.e., subframe # 1). If the RRP starts from subframe #2, the CSI-RS is transmitted after the fourth subframe (i.e., subframe #6) and relatively late. Therefore, there may be a problem when the UE performs channel estimation.

In contrast, if the boundary of the radio frame starts from the time point at which the RRP starts as in fig. 20, the time point at which the RRP starts is always subframe #0, and thus, the CSI-RS is always transmitted in the next subframe (i.e., subframe # 1). Therefore, the location of the CSI-RS transmission resource is regularly determined. Accordingly, the UE can predict a time point at which the CSI-RS is transmitted, and thus, can more efficiently perform channel estimation.

Also, in the case of the CRS, the CRS sequence is differently generated according to a slot number in which the CRS is transmitted. Therefore, if the subframe index of the reference cell is equally applicable in the RRP of the cell in the unlicensed band/spectrum, the CRS sequence is differently generated according to the slot number in which the CRS is transmitted. In this case, there is a disadvantage that it is difficult for the UE to accurately detect the CRS if the boundary of the subframe or symbol is not accurately aligned with the reference cell.

In contrast, as shown in fig. 20, if the index of the subframe in which the CRS is detected is #0 and the slot number is #0, the eNB always transmits the CRS based on the slot number 0 at a time point on which the RRP starts. Therefore, the UE can detect the CRS more accurately because it performs blind detection on the CRS sequence based on slot number 0.

Fig. 21 is a diagram illustrating a floating radio frame boundary according to an embodiment of the present invention.

In fig. 21, a first cell represents a reference cell (e.g., a PCell or a specific serving cell in a licensed band), and a second cell represents a cell in which an RRP has been configured in an unlicensed band/spectrum.

In addition to the aforementioned blind detection of the floating radio frame boundary, the UE may perform an operation for increasing the radio frame number (n _ f) parameter at a specific interval (e.g., an interval of 10ms) with reference to the PCell timing or the timing of a specific reference cell (e.g., a specific cell configured by the eNB or previously defined as described above) in the corresponding LTE-U band.

For example, as shown in fig. 21(a), the UE may equally increase the value of the radio frame number "n _ f" parameter with the radio frame number of the reference cell in the LTE-U band.

Accordingly, regardless of an increase in subframe index and the number of symbols in the LTE-U band, the value of the radio frame number (n _ f) parameter may be increased in the LTE-U band at the same point in time at which the value of the parameter "n _ f" in the reference cell is increased. That is, both the subframe index and the slot number are increased from #0 because the floating radio frame boundary is determined at the time point at which it is obtained by blind detection, but the next radio frame boundary may follow the timing of the reference cell.

Further, as shown in fig. 21(b), the UE may increase the value of the radio frame number (n _ f) parameter in the LTE-U band independent of the reference cell.

The value of the radio frame number (n _ f) parameter itself is incremented at fixed intervals (e.g., 10ms) as is continued with conventional techniques (the first cell in fig. 21).

Further, when the UE obtains a floating radio frame boundary in the LTE-U band via blind detection, both the subframe index and the slot number increase from #0 at the corresponding time point. Further, the value of the radio frame number (n _ f) parameter may remain the same value without change until the time period (e.g., 10ms) of one radio frame is terminated in the LTE-U band from this time.

That is, in the case where the value of the radio frame number (n _ f) parameter is increased at fixed intervals, when the floating radio frame boundary is obtained by blind detection in the value state of a specific value of the parameter "n _ f" (in fig. 21(b) — "n"), the slot number is initialized to #0 from the corresponding time point. Further, when the slot number increases to #19, the current value of the radio frame number (n _ f) parameter ("n" in fig. 21 (b)) is kept as it is. The value of the radio frame number (n _ f) parameter is increased again ("n + 1" in fig. 21 (b)) until the next slot number becomes #0 again.

Such an operation is applied until a point of time at which the corresponding RRP is terminated. The value of the radio frame number (n _ f) parameter follows the value of the parameter "n _ f" (i.e., the value of the parameter "n _ f" in the reference cell) fixed at fixed intervals from the time point at which the RRP is terminated. Also, the subframe index and slot number in the reference cell may be used from a time point at which the RRP is terminated.

Accordingly, regardless of the radio frame number of the CC (or cell) in the LTE-a band, the radio frame number of the CC (or cell) in the LTE-U band increases at the radio frame interval of the LTE-a band from the boundary of the floating radio frame.

If CAs of a plurality of CCs (or cells) are configured in the LTE-U band in the UE, an operation for separately determining a floating radio frame boundary from a radio frame boundary fixed in the LTE-U band as described above may be applied to each CC (or cell) configured in the LTE-U band. That is, the RRP may be independently determined for each CC (or cell) configured in the LTE-U band, and the boundary of the radio frame may be independently determined from a time point at which the RRP predetermined thereon starts.

Via this method, the UE may not perform blind detection during a particular time (e.g., X milliseconds) from the moment when the UE obtains a floating radio frame boundary via blind detection. That is, the blind detection operation may be stopped during a specific time. Further, the UE may be defined or configured to recognize that the RRP is maintained for at least a certain time and perform normal downlink reception and uplink transmission operations.

In this case, the specific time may be previously defined in a radio frame, subframe, or slot unit, or may be set by the eNB. As a representative example, the specific time may be X-5 (milliseconds), or may be predefined as X-10 (milliseconds), or may be set by the eNB. In some embodiments, the specific time may be predefined as other values or may be set by the eNB.

In this case, if CAs of a plurality of CCs (or cells) are configured in the UE in the LTE-U band, a specific time during which the UE does not perform blind detection on each CC (or cell) may be independently determined.

Thus, when the UE acquires a floating radio frame boundary, it does not need to perform blind detection during at least X times milliseconds. Therefore, there is an advantage in that the power consumption of the UE can be reduced.

In addition, resources configured to have a specific periodicity, such as CSI-RS and CSI Interference Measurement (IM), are set as relative subframe offset values with respect to a time point of a radio frame boundary obtained floatingly. Therefore, in an environment where it cannot be guaranteed to obtain a constant RRP, such as the LTE-U band, there is an advantage that the position of a primary resource, such as an RS, can be determined regularly within the obtained RRP.

Further, if the floating radio frame boundary is separately configured from the radio frame boundary fixed in the LTE-U band as described above, in the case where HARQ ACK/NACK is transmitted in another band (e.g., PCell) in addition to the corresponding LTE-U band, there may be a problem in that HARQ timelines (i.e., ACK/NACK transmission timing and retransmission data transmission timing) are tangled due to the floating radio frame boundary.

Furthermore, if CAs of multiple CCs (or cells) are configured in the LTE-U band in the UE, when HARQ ACK/NACK for data transmitted in one CC (or cell) is transmitted in another CC (or cell), the HARQ timeline may be tangled due to floating radio frame boundaries being independently configured for each CC (or cell).

Accordingly, as described above, if different CCs (or cells) support a single signaling operation (e.g., if HARQ ACK/NACK operation is supported), the timeline of the corresponding signaling operation may be determined based on any one of the specific CCs (or cells).

For example, if a timeline of a particular signaling operation (e.g., HARQ timeline) operates with a different CC (or cell), the timeline may be determined based on timing of a reference cell.

These are described in more detail. If different CCs (or cells) and a specific timeline (e.g., HARQ timeline) operate in a specific CC (or cell) configured in the LTE-U band, a subframe index (or slot number) may be determined with reference to timing of a reference cell (e.g., PCell or a specific cell in the grant band). Accordingly, the HARQ timeline may be defined based on subframe indexes #0 to #9 and slot numbers #0 to #19 defined within a radio frame boundary of a fixed interval (e.g., 10 msec) based on the value of the radio frame number "n _ f" parameter increased at a corresponding fixed interval in a corresponding LTE-U band.

For example, in the example of fig. 21(b), it is assumed that the UE receives downlink data in subframe #2 of the radio frame number "n" in the second cell and transmits corresponding ACK/NACK in the first cell. In this case, subframe #2 of the radio frame number "n" in the second cell is the same point of time as subframe #5 of the radio frame number "n" (which increases at fixed intervals) in the first cell (i.e., the reference cell). Accordingly, the UE may transmit ACK/NACK in subframe #9 of the radio frame number "n" (i.e., a subframe subsequent to the fourth subframe) in the first cell (i.e., the reference cell).

Accordingly, if the serving cell in the unlicensed band/spectrum and the cell in the licensed band jointly support the HARQ operation, a time point at which the ACK/NACK is transmitted (or a time point at which the ACK/NACK is repeatedly transmitted) may be determined based on a radio frame boundary of a specific cell in the licensed band.

Also, if CAs of a plurality of CCs (or cells) are configured in the LTE-U band in the UE, the HARQ timeline may be determined based on a radio frame boundary of a specific CC (or cell) in the LTE-U band when HARQ ACK/NACK for data transmitted in one CC (or cell) is transmitted in a different CC (or cell).

Further, the TDD system may be defined or configured to apply subframe indexes fixed at fixed intervals as described above with respect to a subframe index to which UL/DL configuration (refer to table 1) is applied.

For example, in the example of fig. 21(b), in case of a TDD system, the subframe index in table 1 may indicate a subframe index of the first cell. Further, in the second cell, each uplink, downlink, or special subframe may be reserved with reference to a subframe index of the first cell corresponding to the same time point.

Thus, the radio frame number "n _ f", the subframe index and the slot number "n _ s" identified and calculated by the UE may basically include different values of the two groups. Whether the UE independently calculates/maintains parameter values corresponding to the two groups in parallel, and the parameter values that must be applied to any one of the two groups for each specific operation may be defined or configured differently.

For example, in group 1{ radio frame number "n _ f", subframe index and slot number "n _ s" }, as described above, the radio frame number "n _ f" is increased at always constant intervals (e.g., 10ms) based on the timing of a specific reference cell (e.g., PCell or specific serving cell) in the LTE-U band, and subframe indexes #0 to #9 and slot numbers "n _ s" (#0 to #19) are allocated to the corresponding radio frame numbers "n _ f".

Further, in group 2{ radio frame number "n _ f", subframe index, slot number "n _ s" }, as described above, the radio frame number "n _ f" is obtained based on the floating radio frame boundary obtained by blind detection of the UE, and subframe indices #0 to #9 and slot numbers "n _ s" (#0 to #19) are allocated within the floating radio frame obtained as described above. In this case, at the start point of the floating radio frame boundary, the radio frame number "n _ f" in group 1 may continue in the future for a certain time (e.g., X milliseconds).

Operations to be recognized by the UE in a form such as described above, and to which parameters corresponding to each group may be applicable, may be defined or configured differently.

Further, as described above, if CAs of a plurality of CCs (or cells) are configured in the UE in the LTE-U band, the floating radio frame boundary described above may be independently determined for each CC (or cell). Thus, group 2 may be determined for each CC (or cell). That is, in this case, the UE may identify group 1 at timings and a plurality of group 2 increasing at a certain interval in the LTE-U band.

Furthermore, if the blind detection of the floating radio frame boundary fails as in group 2, the subsequent RRP (e.g., during a fixed X milliseconds) cannot be correctly obtained.

Therefore, in order to compensate for such a disadvantage, a method of improving the detection probability of the UE by applying a separate power increase to the preamble/midamble and/or the RS, such as the CRS, in a specific subframe (e.g., subframe #0) within the floating radio frame may be applied.

Further, the application of power increase to the preamble/midamble and/or CRS in a particular subframe within a floating radio frame may be predefined in the UE or may be set by the eNB.

If the CRS power of a specific subframe (e.g., subframe #0) is increased as described above, separate parameters (e.g., P _ a and/or P _ B) to be specifically applied in the corresponding subframe may be provided to the UE. Such parameters may be provided via higher layer signaling. Further, such parameters may be included in the "RRP configuration information" and transmitted.

In this case, P _ a and P _ B are parameters for determining a CRS Energy Per Resource Element (EPRE) and a ratio of PDSCH EPRE for each OFDM symbol. The parameter P _ a is a UE-specific parameter and the parameter P _ B is a cell-specific parameter.

Therefore, the power ratio between PDSCH and CRS (PDSCH-to-CRS power ratio) may be different in OFDM symbols transmitting the corresponding power-increased CRS. The UE is informed of such parameters so that the UE applies the parameters to demodulation of the PDSCH. As described above, the ratio of PDSCH EPRE and CRS EPRE in PDSCH REs may be determined according to the OFDM symbol index and/or the number of CRS transmit antenna ports in each OFDM symbol.

Further, for example, the reference signal power "referenceSignalPower" may be transmitted via higher layer signaling. In this case, the reference signal power parameter provides the downlink RS EPRE. Accordingly, a transmission power of the CRS transmitted in a specific subframe may be determined.

Further, the failure of the special subframe (e.g., subframe #0) having the meaning of the starting subframe of the RRP to become an MBSFN subframe (i.e., the special subframe is always a non-MBSFN subframe) may be defined in advance or may be set by the eNB. Accordingly, detection and demodulation performance of the CRS in the corresponding subframe may be guaranteed at a certain level or more, because the number of OFDM symbols transmitted in the CRS is guaranteed to be at least Z (e.g., Z ═ 4) in the corresponding subframe (i.e., subframe # 0).

The operations for dividing the group of radio frame number "n _ f", subframe index and slot number "n _ s" into group 1 and group 2 (one or more group 2) and determining the floating radio frame boundary as group 2 are applicable without limitation to unlicensed band/spectrum, such as LTE-U band. That is, the operation may be applicable to CA scenarios between generic authorization bands.

In one scenario, such as the case where time domain inter-cell interference coordination (ICIC) is applied, the interference levels of two subframes (e.g., a protected subframe and an unprotected general subframe) may have a large impact on the UE's measurements because the interference levels are significantly different.

Operations of the UE related to the measurements affected as described above include Radio Link Monitoring (RLM) measurements, Radio Resource Management (RRM) measurements (e.g., measurements such as Reference Signal Received Power (RSRP), Received Signal Strength Indication (RSSI), and/or quality of Reference Signal Reception (RSRQ)), and Channel State Information (CSI) measurements (e.g., measurements such as CQI, PMI, RI, and/or PTI).

For restricted measurements, the eNB signals the restricted measurement resource pattern to the UE.

For example, in restricted RLM and RRM measurements for the serving cell, the network may configure a restricted measurement resource pattern in the UE. Therefore, the UE performs the restricted measurement using resources indicated by the restricted measurement resource pattern for the RLM and RRM measurements of the serving cell.

Further, in the restricted RRM measurement for the neighbor cell, the network may configure a measurement resource pattern in the UE different from the restriction of the resource pattern used for the restricted RLM and RRM measurement for the serving cell. Accordingly, the UE performs the restricted measurement using resources indicated by the restricted measurement resource pattern for the restricted RRM measurement on the neighboring cell.

When the restricted measurement resource pattern is configured for RRM measurements on the neighbor cells, a list of physical cell IDs of the corresponding neighbor cells is also provided to the UE. The UE applies the restricted measurements to only the listed cells and applies the generic measurements to the other cells. The reason for this is that unnecessarily restricted measurements are not applied to neighboring cells whose interference is not a problem, and restricted measurements are only applied to neighboring cells whose interference is a problem.

CSI measurements are described below. The UE averages the results of the channel and interference estimation for multiple subframes in order to derive CSI feedback. In order for the UE to not average interference for two different subframe types, the eNB may configure a group of 2 subframes and perform configuration such that the UE averages channel and interference for subframes belonging to one subframe group and does not average different subframe groups. Furthermore, the UE reports individual CSI measurements for a group of 2 subframes. The UE may report CSI measurements periodically according to a reporting period group in each subframe group, or may report one of CSI measurements for a group of two subframes via a PUSCH when the reporting is triggered by a PDCCH.

As described above, the UE may autonomously identify a cell/TP-specific RS (e.g., CRS, CSI-RS, etc.) detected in the LTE-U band and/or a period of a preamble/midamble as an RRP via or without secondary signaling (i.e., RRP configuration information).

That is, the UE may directly determine the RRP via the aforementioned blind detection operation in the LTE-U band, except for the case where the scheduling grant is separately received from the eNB. Accordingly, the UE may perform CSI, RRM, and/or RLM measurements on the RRP determined as described above in a restricted measurement form within the RRP.

The reason for this is that correct measurement operations in the LTE-U band according to unpredictable variations of the RRP cannot be performed using the restricted measurement only on conditions performed on a specific subframe group as semi-statically provided in the existing restricted measurement.

Thus, the UE may perform CSI, RRM and/or RLM limited measurements only in subframes corresponding to the subframe groups, where the CSI, RRM and/or RLM measurements must be performed within the RRP determined by blind detection. The subframe group or period for which the restricted measurement is performed is hereinafter simply referred to as "restricted measurement object" as described above.

Hereinafter, the operation of the UE for such a RRP-related limited measurement method is described below.

Referring to fig. 22, the eNB transmits configuration information for restricted measurement to the UE at step S2201.

The configuration information for the restricted measurements is necessary for the UE to perform CSI, RRM, and/or RLM restricted measurements within the RRP of the unlicensed band/spectrum.

Configuration information for the restricted measurements may be transmitted to the UE via higher layer signaling (e.g., RRC signaling) or dynamic indication (e.g., DCI including a corresponding aperiodic CSI trigger).

The configuration information for the restricted measurements may include restricted measurement objects, i.e., the restricted measurements are time periods or subframes, which are objects on which the UE will perform CSI, RRM, and/or RLM restricted measurements.

Further, the configuration information may include information for enabling the UE to determine the restricted measurement object. For example, a specific threshold related to an average received power with respect to a specific RS (e.g., CRS or CSI-RS) for a measurement object for which the UE performs restriction in a specific time unit (e.g., subframe or OFDM symbol) may correspond to the configuration information.

If the restricted measurement object and the configuration information are used for the restricted measurement, a threshold such as RS may be defined in advance. In this case, configuration information for the restricted measurement cannot be provided by the eNB. That is, step S2201 may be omitted.

The UE performs measurement using a specific RS (e.g., CRS, CSI-RS, etc.) among the measurement objects restricted within the RRP at step S2202, and reports the measurement result to the eNB at step S2203.

These are described in more detail. CSI and/or RRM measurements in a particular CC, such as the LTE-U band, may be defined or may be set by the eNB such that limited measurements are performed only for the time period determined to be a RRP, through blind detection of the preamble/midamble (e.g., SS) and/or the RS of the UE, based on or without separate auxiliary signaling.

In this case, specific subframe group information (i.e., restricted measurement configuration information), such as CSI process configuration, may be transmitted to the UE. The restricted measurement may be configured by the eNB or may be predefined for each subframe group. In this case, the UE may average the measured estimates for each respective group of subframes and for only one RRP. That is, the UE averages the results of channel and interference estimation measurements in subframes belonging to one subframe group within one RRP.

In another embodiment, after the UE performs blind detection on a specific RS (e.g., CRS, CSI-RS, etc.), information on a specific threshold value determining a restricted measurement object (i.e., restricted measurement configuration information) may be provided to the UE only when the average received power is greater than or equal to the specific threshold value.

Such thresholds are parameters of the measurement with respect to the respective restrictions and may be provided separately from the restricted measurement configuration information.

For example, the threshold value may be indicated in units of subframes. In this case, when the average reception power value of the RS REs within each subframe within one RRP is greater than or equal to the corresponding threshold value, the UE may determine that the corresponding subframe belongs to the restricted measurement object. Further, the UE may average the measurement estimation values in the restricted measurement objects and may report the average value to the eNB.

As described above, the RRP is defined to be basically not limited to a single continuous period of time, but may be defined in the form of a set of a plurality of continuous periods of time.

In this case, a period of time such as a subframe unit satisfying the threshold or more may be represented in the form of a set of a plurality of consecutive periods of time. Thus, in this case, the measurement estimate may be defined separately by the maximum time period window of the respective limited measurement averages or may be set by the eNB. In this case, if the maximum period window is set by the eNB, it may be transmitted to the UE as limited measurement configuration information.

For example, if the corresponding maximum time period window is t (ms), it is defined as a measurement estimate that the UE can average the measurements for the corresponding limit with respect to all of the plurality of discontinuous subframes (which meet the threshold condition during the time period).

As described above, the RRP may determine a floating radio frame boundary, and the radio frame number "n _ f", the subframe index, and the slot number "n _ s" may be divided into two groups. In this case, the restricted measurement object configured by the UE may be determined based on the timing according to the fixed radio frame boundary, that is, the radio frame number "n _ f", the subframe index, and the slot number "n _ s". For example, a restricted measurement object configured in the UE may be determined with reference to a subframe index determined at a fixed interval, and the UE may perform measurement in a subframe of an unlicensed band/spectrum corresponding to the same point in time.

Conventional apparatus to which embodiments of the present invention may be applied

Referring to fig. 23, the wireless communication system includes one eNB 2310, and a plurality of UE2320 units located within range of the eNB 2310.

The eNB 2310 includes a processor 2311, a memory 2312, and a Radio Frequency (RF) unit 2313. The processor 2311 performs the functions, processes and/or methods set forth in fig. 1 through 22. The radio interface protocol layers may be executed by the processor 2311. The memory 2312 is connected to the processor 2311 and stores various information units for driving the processor 2311. The RF unit 2313 is connected to the processor 2311 and transmits and/or receives a radio signal.

The UE2320 includes a processor 2321, a memory 2322, and an RF unit 2323. The processor 2321 performs the functions, processes and/or methods set forth in fig. 1 through 22. The radio interface protocol layers may be executed by the processor 2321. The memory 2322 is connected to the processor 2321, and stores various information units for driving the processor 2321. The RF unit 2323 is connected to the processor 2321 and transmits and/or receives a radio signal.

The

memory

2312, 2322 may be internal or external to the

processors

2311, 2321, and connected to the

processors

2311, 2321 by various well-known means. Further, the eNB 2310 and/or the UE2320 may have a single antenna or multiple antennas.

In the foregoing description of the embodiments, elements and features of the invention have been combined in specific forms. Each of the elements or features may be considered optional unless explicitly described otherwise. Each of the elements or features may be implemented in such a manner as not to be combined with other elements or features. In addition, some of the elements and/or features may be combined to form embodiments of the invention. The order of operations described in connection with the embodiments of the invention may be changed. Some elements or features of an embodiment may be included in another embodiment or may be replaced with corresponding elements or features of another embodiment. It is obvious that the embodiments may be constituted by claims which are incorporated in claims without explicit citation or may be included as new claims by amendment after the application is filed.

Embodiments of the invention may be implemented by various means, for example, in hardware, firmware, software, or a combination thereof. In the case of implementation by hardware, embodiments of the invention may be implemented using one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, and/or microprocessors.

In the case of implementation by firmware or software, the embodiments of the present invention may be implemented in the form of a module, a procedure, or a function that performs the aforementioned functions or operations. The software codes may be stored in a memory and driven by a processor. The memory may be provided inside or outside the processor, and may exchange data with the processor via various well-known means.

It will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The detailed description is, therefore, not to be taken in a limiting sense, but rather, is to be taken in an illustrative sense. The scope of the invention is to be determined by reasonable analysis of the appended claims, and all changes that come within the meaning and range of equivalency of the invention are intended to be embraced therein.

Industrial applicability

According to the embodiments of the present invention, a scheme of transmitting and receiving data in an unlicensed band in a wireless communication system has been mainly illustrated as being applicable to a 3GPP LTE/LTE-a system, but may be applicable to various wireless communication systems in addition to the 3GPP LTE/LTE-a system.

Claims

1. A method of measuring a channel by a user equipment, UE, in an unlicensed band in a wireless communication system, the method comprising:

measuring a channel based on a Reference Signal (RS) received from a Base Station (BS) in a cell of an unlicensed band,

wherein channel measurements based on RSs in a plurality of subframes included in a time period are averaged,

wherein the time period is a continuous time period occupied by the BS based on a channel access procedure for data transmission in a cell of an unlicensed band.

2. The method of claim 1, further comprising: receiving configuration information including parameters for blind detection of the RS and/or for determining the time period from the BS.

3. The method of claim 2, wherein the configuration information comprises one or more of a sequence scrambling initialization parameter of a signal, information identifying a radio frame boundary in a cell of the unlicensed band, information about a transmission bandwidth of the signal, information about a power level threshold used to determine the time period, a number of antenna ports in which a signal is transmitted, a Multicast Broadcast Single Frequency Network (MBSFN) subframe configuration, quasi co-location (QCL) capable assumed RSs, and a large scale characteristic of a wireless channel.

4. The method according to claim 3, wherein, if the power level threshold is set in a subframe unit, a subframe in which an average reception power value of resource elements in which signals are transmitted is greater than or equal to the power level threshold is determined to belong to the time period.

5. The method of claim 3, wherein if the power level threshold is set in an Orthogonal Frequency Division Multiplexing (OFDM) symbol unit, a subframe in which the number of OFDM symbols in which an average received power value of resource elements in which a signal is transmitted is greater than or equal to the power level threshold is greater than or equal to a certain number is determined to belong to the time period.

6. The method of claim 3, wherein the QCL-capable reference signals comprise reference signals transmitted in cells of a licensed band.

7. The method of claim 6, wherein the Doppler shift value of the cell of the unlicensed band is derived by correcting a Doppler shift estimate estimated from a reference signal transmitted in the cell of the licensed band based on a ratio between a center frequency of the cell of the licensed band and a center frequency of the cell of the unlicensed band.

8. The method of claim 1, wherein a boundary of a floating radio frame is determined with respect to a cell of the unlicensed band from a time point of detecting a signal or after a specific time from the time point of detecting a signal.

9. The method of claim 8, wherein the radio frame number of the cell of the unlicensed band is sequentially increased at the same interval as that of the radio frame of the licensed band from the boundary of the floating radio frame without considering the radio frame number of the cell of the licensed band.

10. The method of claim 8, wherein a blind detection operation for detecting the signal is stopped for a certain time from a point of time when the boundary of the floating radio frame is obtained by blind detection.

11. The method of claim 8, wherein if both the cell of the unlicensed band and the cell of the licensed band support hybrid automatic repeat request (HARQ) operation, determining a timeline for the HARQ based on radio frame boundaries of the cell of the licensed band.

12. The method of claim 1, wherein a power increase is applied to a signal transmitted in a first subframe of the time period.

13. The method of claim 1, wherein channel measurements are performed in restricted measurement objects during the time period.

14. The method of claim 13, wherein the restricted measurement object is set by the BS or determined within the time period as a subframe in which an average received power of the RS is greater than or equal to a certain threshold.

15. The method of claim 14, wherein, if the time period is a discontinuous time period, the restricted measurement object is determined as a subframe in which an average received power of the RS is greater than or equal to a certain threshold value within a Reserved Resource Period (RRP) within a certain time window.

16. A user equipment for measuring a channel in an unlicensed band in a wireless communication system, the user equipment comprising:

a Radio Frequency (RF) unit configured to transmit and receive a radio signal; and

a processor configured to control the user equipment,

wherein the processor measures a channel based on a Reference Signal (RS) received from a Base Station (BS) in a cell of the unlicensed band,